Can you use Windows 8 WinRT API from .NET Desktop applications?

Over the course of time I received a number of comments on my blog in this area. Many questions were asked like “Can you use WinRT from Desktop applications?”, “Can you use WinRT from .NET applications?”, etc..

Well, the answer is YES. It is possible to use WinRT from Desktop applications. WinRT APIs may be tied to Metro style apps, Desktop apps or potentially available to both. The documentation will list which environments (Desktop, Metro style or both) a given API works in.

Note: Custom WinRT components are only supported in Metro style applications. They are not supported in Desktop applications.

For ex, WinRT has an API for Accelerometer. The Accelerometer class represents an accelerometer sensor which returns G-force values with respect to the x, y, and z axes.

Namespace: Windows.Devices.Sensors namespace

Class: Accelerometer

If we open the API documentation at http://msdn.microsoft.com/en-us/library/windows/apps/windows.devices.sensors.accelerometer.aspx, see the section Applies to: Metro style apps | desktop apps. Which means this class works in Metro Apps as well as desktop apps.

Figure 1: MSDN documentation showing WinRT API and it’s applies to section.

Internals (Deep dive) of Metro Application calling WinRT Component DLL

We have created a C++ XAML application that consumes the WinRT C++ DLL in part 1

we have seen the compiler generated components when we compile a WinRT Component DLL.  Part2  discusses how the C# application interacts with the C++ WinRT component.

We have seen the packaging and installation process that happens in the background during building and deploying of the applications here Under the hood Part 3 : WinRT, Windows 8, C++, C#.NET, Metro, WinRT Component DLL

We have seen the C++ XAML application calling the C++ WinRT Component DLL here Under the hood Part 4 : C++ WinRT Component DLL & C++ XAML application – WinRT, Windows 8, C++, Metro

Part5 discusses developing JavaScript application that consumes WinRT Component DLL

Lets dig deeper into how the C++ Application makes  a call across the WinRT Application Binary Interface to access the class methods inside the WinRT DLL. The slide in fig 1 is taken from the build conference which shows the internals of the method calls. We will examine the ABI and how C++ compiler extensions help reference that ABI without exposing the internal details of dealing with COM interfaces and COM activation.

Download the source code from here.

Fig 1: Slide showing the flow of the method calls across the boundaries.

A WinRT component implements the IInspectable interface, which is derived from IUnknown. IInspectable is used by the dynamic language bindings from JavaScript. Given a reference to a WinRT component, the JavaScript interpreter can call the IInspectable::GetRuntimeClassName method and obtain the fully-qualified class name of the WinRT component. Using the namespace name the interpreter can ask Windows to load the metadata file (.winmd) describing the component, and from the metadata determine how to use the interfaces implemented by the component.

When WinRT components are accessed from C++ or from .NET languages, there is no need for the IInspectable interface – IUnknown::QueryInterface suffices for all intents and purposes. In fact, .NET “interop” with WinRT relies on simple COM interop – an RCW created by the CLR manages the lifetime of the underlying WinRT component. For C++ language bindings, the story is somewhat more complicated, and the language extensions come into play.

The left side in Fig 1 is the C++ client application code which calls the method in right side WinRT DLL. So here if the method in C++ DLL throws an exception, it should be caught by the C++ application. But it’s not a good practice throw exceptions directly across boundaries.

The left side call (C++ Client App: Consumer) to Add() method causes the compiler to create an inline native to COM wrapper method. Also, on the left hand side, COM HRESULTs are converted to exceptions and COM “retval” arguments are converted to return values. The Add() method makes a call to this wrapper method. This inline methods generated will be something like a COM method that we write in COM components. We can see the source code generated by the compiler using some compiler switch options. we have seen the compiler generated components for making the C# application access the C++ WinRT component here Under the hood Part 2 : C++ WinRT Component DLL & C#.NET Metro application.

From the WinMD file, the C++ application knows the WinRT API signature(shown at the top of the slide) and makes the appropriate call across the WinRT ABI.

HRESULT __stdcall Add(Calculator* this, int i, int j, int * result)

//On the LHS Application, the native to COM Wrapper is as follows (Consumer-side stub pseudo-code) . See the last section of this post to see the compiler generated code. 
inline int Add(int i, int j) {
int res;
HRESULT hr = __cli_Add(this, i, j, &res);
if (hr != 0) {

__throw_hr_as_exception(hr); }
return res;
}

On the right hand side too (C++ Component DLL), C++ compiler generates inline functions. Also, WinRT and C++ exceptions are converted to HRESULTs and return values are converted to “retval” arguments. Note that the only HRESULT, which does not represent an exceptional condition, is S_OK (numeric value 0). No more positive HRESULTs (such as S_FALSE) that need to be checked explicitly by the caller.

//On the RHS C++ Component, COM to Native Wrapper stub pseudo-code is as follows:
HRESULT __stdcall ___cli_Add(Calculator* calc,
int i, int j, int* result) {
try { *result = calc->Add(i, j); }
catch(Platform::Exception^ e) { return e->HResult; }
return S_OK;
}

See the last section of this post to see the compiler generated code.

By the way, the inline wrappers can be called directly, bypassing the C++ language extensions.

The C++ language extensions (enabled by the /ZW switch) map WinRT to standard C++ patterns like constructors, destructors, class methods, and exceptions. For example, the language extensions hide the COM-style activation (RoActivateInstance) behind a constructor call (albeit with the ref new keyword), and hide reference counting (IUnknown::AddRef and Release) by automatically managing references. The syntax of these extensions is very similar to C++/CLI

Code Snippet

    CalculatorSample^ calcobj = ref new  CalculatorSample();
    txtAddResult->Text = calcobj->Add(10,20).ToString();

In the above code snippet, you can see we created the object of CalculatorSample class which is present in WinRT C++ Component using ref new. If you know COM, this is something like cocreateinstance() but its more than that. For now, use ref new to create objects of WinRT classes.

Let us see how to skip to exception wrapper and directly calling the Add() method present in WinRT Component. Every function in the class has a low level equivalent inside the class and currently it is prefixed with __cli_ and it takes the output as last parameter. So using ToString() on an integer. So this is another way of calling the methods inside the WinRT components. If we need HResult, we need reference to windows.h. For that include Windows.h in pch.h file as shown below.

Code Snippet

//
// pch.h
// Header for standard system include files.
//

#pragma once

#include <Windows.h>
#include "App.xaml.h"

The complete code to call the WinRT component method is as follows.

Code Snippet

MainPage::MainPage()
{
    InitializeComponent();

    CalculatorSample^ calcobj = ref new  CalculatorSample();
    //txtAddResult->Text = calcobj->Add(10,20).ToString();

    // declare a stack variable to hold the value of the result
    int result;
    //call into  calc object low level __cli_Add() but no intellisense in this preview
    HRESULT hr = calcobj->__cli_Add(10,20,&result);

    //typedef HRESULT (__std

    txtAddResult->Text = result.ToString();
}

 

Another (3rd) way is to use function pointers and call the methods using pointers. Basically, we we can take the calculator^ object, which is a pointer to a pointer to a vtable and reinterpret cast it so that it has a pointer to virtual function, which are vtables. Then we can find out the location of the method we need to call using some compiler switches which I will show below. For the Add function, we are going to specifically pick the sixth function of that and call into it. In the class layout mentioned below, I highlighted the member at 6th location. reinterpret_cast takes the calcobj ^ and cast it to a pointer to a pointer, that’s it. This is how the functions inside the components are called internally at a low level.

Code Snippet

MainPage::MainPage()
{
    InitializeComponent();

    CalculatorSample^ calcobj = ref new  CalculatorSample();
    //txtAddResult->Text = calcobj->Add(10,20).ToString();

    // declare a stack variable to hold the value of the result
    int result;
    //call into  calc object low level __cli_Add() but no intellisense in this preview
    //HRESULT hr = calcobj->__cli_Add(10,20,&result);

    //create a c function that actually represent an ABI call we will be making
    //to add function which takes this pointer, 2 input parameters and an out parameter.
    typedef HRESULT (__stdcall* AddFunc_t) (CalculatorSample^ calc, int i, int j, int * result);
    //now we can take the calculator^ object, which is a pointer to a pointer to a vtable
    //and reinterpret cast it so that it can say ok now i have a pointer of  virtual function
    //which are vtables and i am going to specifically pick the sixth function of that and call into it.
    //reinterpret_cast takes the calcobj ^ and cast it to a pointer to a pointer
    AddFunc_t* addFunc = *reinterpret_cast<AddFunc_t**>(calcobj);
    addFunc[6](calcobj,10,20, &result);

    txtAddResult->Text = result.ToString();
}

Basically a hat is a pointer to a pointer to an array of function pointers, which is Pointer to vptr to vtable. Hat (^) provides automatic reference counting.

To find out the class layout, use the /d1reportSingleClassLayout<class name> compiler switch option. Right click on the WinRTComponent.cpp file in C++ WinRT Component DLL project and select Command Line which is under C/C++. In the Additional Options, mention /d1reportSingleClassLayoutCalculatorSample, click ok and compile the project. See the output window for the magic. There is also another option to see all classes layout by using the option /d1reportAllClassLayout.

 

1>—— Rebuild All started: Project: CppWinRTComponentDll, Configuration: Debug Win32 ——
pch.cpp
WinRTComponent.cpp
class __ICalculatorSamplePublicNonVirtuals    size(4):
    +—
    | +— (base class Object)
0    | | {vfptr}
    | +—
    +—

__ICalculatorSamplePublicNonVirtuals::$vftable@:
    | &__ICalculatorSamplePublicNonVirtuals_meta
    |  0
0    | &Object::__cli_QueryInterface
1    | &Object::__cli_AddRef
2    | &Object::__cli_Release
3    | &Object::__cli_GetIids
4    | &Object::__cli_GetRuntimeClassName
5    | &Object::__cli_GetTrustLevel
6    | &__ICalculatorSamplePublicNonVirtuals::__cli_Add
7    | &__ICalculatorSamplePublicNonVirtuals::Add

__ICalculatorSamplePublicNonVirtuals::Add this adjustor: 0
__ICalculatorSamplePublicNonVirtuals::__cli_Add this adjustor: 0

class __CalculatorSampleActivationFactory    size(12):
    +—
    | +— (base class IActivationFactory)
    | | +— (base class Object)
0    | | | {vfptr}
    | | +—
    | +—
    | +— (base class Object)
4    | | {vfptr}
    | +—
8    | __cli_MultiThreadedRefCount __cli_refcount
    +—

__CalculatorSampleActivationFactory::$vftable@Object@:
    | -4
0    | &thunk: this-=4; goto __CalculatorSampleActivationFactory::__cli_QueryInterface
1    | &thunk: this-=4; goto __CalculatorSampleActivationFactory::__cli_AddRef
2    | &thunk: this-=4; goto __CalculatorSampleActivationFactory::__cli_Release
3    | &thunk: this-=4; goto __CalculatorSampleActivationFactory::__cli_GetIids
4    | &thunk: this-=4; goto __CalculatorSampleActivationFactory::__cli_GetRuntimeClassName
5    | &thunk: this-=4; goto __CalculatorSampleActivationFactory::__cli_GetTrustLevel

__CalculatorSampleActivationFactory::$vftable@IActivationFactory@:
    | &__CalculatorSampleActivationFactory_meta
    |  0
0    | &__CalculatorSampleActivationFactory::__cli_QueryInterface
1    | &__CalculatorSampleActivationFactory::__cli_AddRef
2    | &__CalculatorSampleActivationFactory::__cli_Release
3    | &__CalculatorSampleActivationFactory::__cli_GetIids
4    | &__CalculatorSampleActivationFactory::__cli_GetRuntimeClassName
5    | &__CalculatorSampleActivationFactory::__cli_GetTrustLevel
6    | &__CalculatorSampleActivationFactory::__cli_Platform_IActivationFactory____cli_ActivateInstance
7    | &__CalculatorSampleActivationFactory::ActivateInstance

__CalculatorSampleActivationFactory::ActivateInstance this adjustor: 0
__CalculatorSampleActivationFactory::__cli_QueryInterface this adjustor: 0
__CalculatorSampleActivationFactory::__cli_AddRef this adjustor: 0
__CalculatorSampleActivationFactory::__cli_Release this adjustor: 0
__CalculatorSampleActivationFactory::__cli_GetIids this adjustor: 0
__CalculatorSampleActivationFactory::__cli_GetRuntimeClassName this adjustor: 0
__CalculatorSampleActivationFactory::__cli_GetTrustLevel this adjustor: 0
__CalculatorSampleActivationFactory::__cli_Platform_IActivationFactory____cli_ActivateInstance this adjustor: 0

class CalculatorSample    size(12):
    +—
    | +— (base class __ICalculatorSamplePublicNonVirtuals)
    | | +— (base class Object)
0    | | | {vfptr}
    | | +—
    | +—
    | +— (base class Object)
4    | | {vfptr}
    | +—
8    | __cli_MultiThreadedRefCount __cli_refcount
    +—

CalculatorSample::$vftable@__ICalculatorSamplePublicNonVirtuals@:
    | &CalculatorSample_meta
    |  0
0    | &CalculatorSample::__cli_QueryInterface
1    | &CalculatorSample::__cli_AddRef
2    | &CalculatorSample::__cli_Release
3    | &CalculatorSample::__cli_GetIids
4    | &CalculatorSample::__cli_GetRuntimeClassName
5    | &CalculatorSample::__cli_GetTrustLevel
6    | &CalculatorSample::

__cli_CppWinRTComponentDll___ICalculatorSamplePublicNonVirtuals____cli_Add
7    | &CalculatorSample::Add

CalculatorSample::$vftable@Object@:
    | -4
0    | &thunk: this-=4; goto CalculatorSample::__cli_QueryInterface
1    | &thunk: this-=4; goto CalculatorSample::__cli_AddRef
2    | &thunk: this-=4; goto CalculatorSample::__cli_Release
3    | &thunk: this-=4; goto CalculatorSample::__cli_GetIids
4    | &thunk: this-=4; goto CalculatorSample::__cli_GetRuntimeClassName
5    | &thunk: this-=4; goto CalculatorSample::__cli_GetTrustLevel

CalculatorSample::Add this adjustor: 0
CalculatorSample::__cli_QueryInterface this adjustor: 0
CalculatorSample::__cli_AddRef this adjustor: 0
CalculatorSample::__cli_Release this adjustor: 0
CalculatorSample::__cli_GetIids this adjustor: 0
CalculatorSample::__cli_GetRuntimeClassName this adjustor: 0
CalculatorSample::__cli_GetTrustLevel this adjustor: 0
CalculatorSample::__cli_CppWinRTComponentDll___ICalculatorSamplePublicNonVirtuals____cli_Add this adjustor: 0

Analyzing the layout:

Every WinRT object is laid out in the following way. The first 3 methods in the Vtable are from IUnknown and the next 3 interfaces methods are there for dynamic languages. The important one is GetRuntimeClassName and it allows JavaScript to call into .net  obtain the fully-qualified class name of the WinRT component. When JavaScript calls GetRuntimeClassName, it returns  CppWinRTComponentDll. CalculatorSample. JavaScript then goes and finds out which WinMD file in the system has the classname CppWinRTComponentDll.CalculatorSample. so Windows 8 will inform that it is inside CppWinRTComponentDll.DLL. It then loads the WinMD file of CppWinRTComponentDll.DLL and calls the Add function inside it. In C++, we don’t use these methods as we can directly interact with the class. It doesn’t do dynamic dispatch.

0 | &CalculatorSample::__cli_QueryInterface
1 | &CalculatorSample::__cli_AddRef
2 | &CalculatorSample::__cli_Release

3 | &CalculatorSample::__cli_GetIids
4 | &CalculatorSample::__cli_GetRuntimeClassName
5 | &CalculatorSample::__cli_GetTrustLevel

6 | &CalculatorSample::

__cli_CppWinRTComponentDll___ICalculatorSamplePublicNonVirtuals____cli_Add

 

Coming to the calculator class, you notice CalculatorSample is of size 12. The first vprt we have is ICalculatorSamplePublicNonVirtuals and then we have vprt to Object and then the ref count.

class CalculatorSample size(12):
+—
| +— (base class __ICalculatorSamplePublicNonVirtuals)
| | +— (base class Object)
0 | | | {vfptr}
| | +—
| +—
| +— (base class Object)
4 | | {vfptr}
| +—
8 | __cli_MultiThreadedRefCount __cli_refcount
+—

If we analyze the first vptr, it points to ICalculatorSamplePublicNonVirtuals. The layout of the interface is as follows. The first 3 methods are for IUnknown and the other 3 are IInspectable. Notice 6 and 7 are referencing the Add method we wrote in the DLL. There are here for a reason. No 7 is to support compile time inheritance. The C++ can directly call into C++.

CalculatorSample::$vftable@__ICalculatorSamplePublicNonVirtuals@:
| &CalculatorSample_meta
| 0
0 | &CalculatorSample::__cli_QueryInterface
1 | &CalculatorSample::__cli_AddRef
2 | &CalculatorSample::__cli_Release
3 | &CalculatorSample::__cli_GetIids
4 | &CalculatorSample::__cli_GetRuntimeClassName
5 | &CalculatorSample::__cli_GetTrustLevel
6 | &CalculatorSample::__cli_CppWinRTComponentDll___ICalculatorSamplePublicNonVirtuals____cli_Add
7 | &CalculatorSample::Add

To understand more, let us use the compiler option. right click on WinRTComponent.cpp and add /d1ZWtokens as shown below and compile the WinRTComponent.cpp class.

In the output window, search for __cli_CppWinRTComponentDll___ICalculatorSamplePublicNonVirtuals____cli_Add and see the inline code generated by the compiler. This gives us a better understanding of the inner workings of calling the WinRT components.

 

1>—— Build started: Project: CppWinRTComponentDll, Configuration: Debug Win32 ——
1>  WinRTComponent.cpp
1>  Declaring Member 2: __ICalculatorSamplePublicNonVirtuals::Add (int __cdecl CppWinRTComponentDll::__ICalculatorSamplePublicNonVirtuals::Add(int,int)). [isVirtual=1 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: __ICalculatorSamplePublicNonVirtuals::__cli_Add (long __stdcall CppWinRTComponentDll::__ICalculatorSamplePublicNonVirtuals::__cli_Add(int,int,int *)). [isVirtual=1 isPure=1 isStatic=0]
1> 
1>  Declaring Member 4a: CalculatorSample::__cli_refcount
1> 
1>  Declaring Member 2: CalculatorSample::__cli_QueryInterface (long __stdcall CppWinRTComponentDll::CalculatorSample::__cli_QueryInterface(class Platform::Guid %,void **)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: CalculatorSample::__cli_AddRef (unsigned long __stdcall CppWinRTComponentDll::CalculatorSample::__cli_AddRef(void)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: CalculatorSample::__cli_Release (unsigned long __stdcall CppWinRTComponentDll::CalculatorSample::__cli_Release(void)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: CalculatorSample::__cli_GetIids (long __stdcall CppWinRTComponentDll::CalculatorSample::__cli_GetIids(unsigned long *,class Platform::Guid **)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: CalculatorSample::__cli_GetRuntimeClassName (long __stdcall CppWinRTComponentDll::CalculatorSample::__cli_GetRuntimeClassName(struct __cli_HSTRING__ **)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: CalculatorSample::__cli_GetTrustLevel (long __stdcall CppWinRTComponentDll::CalculatorSample::__cli_GetTrustLevel(enum __cli_TrustLevel *)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: CalculatorSample::__cli_CppWinRTComponentDll___ICalculatorSamplePublicNonVirtuals____cli_Add (long __stdcall CppWinRTComponentDll::CalculatorSample::__cli_CppWinRTComponentDll___ICalculatorSamplePublicNonVirtuals____cli_Add(int,int,int *)=long __stdcall CppWinRTComponentDll::__ICalculatorSamplePublicNonVirtuals::__cli_Add(int,int,int *)). [isVirtual=1 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: IActivationFactory::__cli_ActivateInstance (long __stdcall Platform::IActivationFactory::__cli_ActivateInstance(class Platform::Object ^*)). [isVirtual=1 isPure=1 isStatic=0]
1> 
1>  Declaring Member 2: __CalculatorSampleActivationFactory::ActivateInstance (class Platform::Object ^__thiscall CppWinRTComponentDll::__CalculatorSampleActivationFactory::ActivateInstance(void)). [isVirtual=1 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: __CalculatorSampleActivationFactory::CreateFactory (long __stdcall CppWinRTComponentDll::__CalculatorSampleActivationFactory::CreateFactory(unsigned int *,struct __cli___classObjectEntry *,class Platform::Guid %,struct __cli_IUnknown **)). [isVirtual=0 isPure=0 isStatic=1]
1> 
1>  Declaring Member 2: __CalculatorSampleActivationFactory::GetTargetClassName (const wchar_t *__stdcall CppWinRTComponentDll::__CalculatorSampleActivationFactory::GetTargetClassName(void)). [isVirtual=0 isPure=0 isStatic=1]
1> 
1>  Declaring Member 4a: __CalculatorSampleActivationFactory::__cli_refcount
1> 
1>  Declaring Member 2: __CalculatorSampleActivationFactory::__cli_QueryInterface (long __stdcall CppWinRTComponentDll::__CalculatorSampleActivationFactory::__cli_QueryInterface(class Platform::Guid %,void **)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: __CalculatorSampleActivationFactory::__cli_AddRef (unsigned long __stdcall CppWinRTComponentDll::__CalculatorSampleActivationFactory::__cli_AddRef(void)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: __CalculatorSampleActivationFactory::__cli_Release (unsigned long __stdcall CppWinRTComponentDll::__CalculatorSampleActivationFactory::__cli_Release(void)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: __CalculatorSampleActivationFactory::__cli_GetIids (long __stdcall CppWinRTComponentDll::__CalculatorSampleActivationFactory::__cli_GetIids(unsigned long *,class Platform::Guid **)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: __CalculatorSampleActivationFactory::__cli_GetRuntimeClassName (long __stdcall CppWinRTComponentDll::__CalculatorSampleActivationFactory::__cli_GetRuntimeClassName(struct __cli_HSTRING__ **)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: __CalculatorSampleActivationFactory::__cli_GetTrustLevel (long __stdcall CppWinRTComponentDll::__CalculatorSampleActivationFactory::__cli_GetTrustLevel(enum __cli_TrustLevel *)). [isVirtual=0 isPure=0 isStatic=0]
1> 
1>  Declaring Member 2: __CalculatorSampleActivationFactory::__cli_Platform_IActivationFactory____cli_ActivateInstance (long __stdcall CppWinRTComponentDll::__CalculatorSampleActivationFactory::__cli_Platform_IActivationFactory____cli_ActivateInstance(class Platform::Object ^*)=long __stdcall Platform::IActivationFactory::__cli_ActivateInstance(class Platform::Object ^*)). [isVirtual=1 isPure=0 isStatic=0]
1> 
1>  inline function header symbol: {ctor}
1> 
1>  {
1> 
1>   
1> 
1>  }
1> 
1>  inline function header symbol: {ctor}
1> 
1>  {
1> 
1>   
1> 
1>  }
1>  <TokenStream>
1> 
1>  namespace CppWinRTComponentDll
1> 
1>  {
1> 
1>   inline int :: CppWinRTComponentDll :: __ICalculatorSamplePublicNonVirtuals :: Add ( int x , int y )
1> 
1>    {
1> 
1>      int __cli_returnValue ;
1> 
1>      long __hr = __cli_Add ( x , y , & __cli_returnValue ) ;
1> 
1>      __cli_WinRTThrowError ( __hr ) ;
1> 
1>      return __cli_returnValue ;
1> 
1>     
1> 
1>    }
1> 
1>   
1> 
1>  }
1>  </TokenStream>
1> 
1>  <TokenStream>
1> 
1>  namespace CppWinRTComponentDll
1> 
1>  {
1> 
1>    inline long __stdcall :: CppWinRTComponentDll :: CalculatorSample :: __cli_CppWinRTComponentDll___ICalculatorSamplePublicNonVirtuals____cli_Add ( int x , int y , int * __cli_returnValue )
1> 
1>    {
1> 
1>      long __hr = 0 ;
1> 
1>      * __cli_returnValue = 0 ;
1> 
1>      try
1> 
1>      {
1> 
1>        auto __tempValue = Add ( x , y ) ;
1> 
1>        * __cli_returnValue = __tempValue ;
1> 
1>       
1> 
1>      }
1> 
1>      catch ( :: Platform :: Exception ^ __param0 )
1> 
1>      {
1> 
1>        __hr = __param0 -> HResult ;
1> 
1>       
1> 
1>      }
1> 
1>      catch ( … )
1> 
1>      {
1> 
1>        __hr = -2147467259 ;
1> 
1>       
1> 
1>      }
1> 
1>      return __hr ;
1> 
1>     
1> 
1>    }
1> 
1>   
1> 
1>  }
1>  </TokenStream>
1> 
1>  <TokenStream>
1> 
1>  namespace CppWinRTComponentDll
1> 
1>  {
1> 
1>    long :: CppWinRTComponentDll :: CalculatorSample :: __cli_QueryInterface ( class Platform::Guid % __param0 , void ** __param1 )
1> 
1>    {
1> 
1>      if ( __param0 . Equals ( __uuidof ( __cli_IUnknown ) ) || __param0 . Equals ( __uuidof ( __cli_IInspectable ) ) || __param0 . Equals ( __uuidof ( struct CppWinRTComponentDll::__ICalculatorSamplePublicNonVirtuals ^ ) ) )
1> 
1>      {
1> 
1>        * __param1 = reinterpret_cast < void * > ( static_cast < struct CppWinRTComponentDll::__ICalculatorSamplePublicNonVirtuals ^ > ( this ) ) ;
1> 
1>        __cli_refcount . Increment ( ) ;
1> 
1>        return 0 ;
1> 
1>       
1> 
1>      }
1> 
1>      return -2147467262 ;
1> 
1>     
1> 
1>    }
1> 
1>    unsigned long :: CppWinRTComponentDll :: CalculatorSample :: __cli_AddRef ( )
1> 
1>    {
1> 
1>      long __cli_returnValue = __cli_refcount . Increment ( ) ;
1> 
1>      return ( unsigned long ) __cli_returnValue ;
1> 
1>     
1> 
1>    }
1> 
1>    unsigned long :: CppWinRTComponentDll :: CalculatorSample :: __cli_Release ( )
1> 
1>    {
1> 
1>      long __cli_returnValue = __cli_refcount . Decrement ( ) ;
1> 
1>      if ( ! __cli_returnValue )
1> 
1>      {
1> 
1>        delete this ;
1> 
1>        :: Platform :: Heap :: Free ( reinterpret_cast < void * > ( this ) ) ;
1> 
1>       
1> 
1>      }
1> 
1>      return ( unsigned long ) __cli_returnValue ;
1> 
1>     
1> 
1>    }
1> 
1>    long :: CppWinRTComponentDll :: CalculatorSample :: __cli_GetIids ( unsigned long * __param0 , class Platform::Guid ** __param1 )
1> 
1>    {
1> 
1>      struct __s_GUID __interfaceList [ ] =
1> 
1>      {
1> 
1>       
1> 
1>        {
1> 
1>          -1302793136 , 5274 , 13110 , 160 , 43 , 249 , 241 , 108 , 73 , 159 , 212
1> 
1>        }
1> 
1>       
1> 
1>      } ;
1> 
1>     
1> 
1>      return __winRT :: __winRTRuntime . __getIids ( 1 , __param0 , __interfaceList , __param1 ) ;
1> 
1>     
1> 
1>    }
1> 
1>    long :: CppWinRTComponentDll :: CalculatorSample :: __cli_GetRuntimeClassName ( struct __cli_HSTRING__ ** __param0 )
1> 
1>    {
1> 
1>      return __winRT :: __winRTRuntime . __windowsCreateString ( ( const wchar_t * ) L"CppWinRTComponentDll.CalculatorSample" , 37 , __param0 ) ;
1> 
1>     
1> 
1>    }
1> 
1>    long :: CppWinRTComponentDll :: CalculatorSample :: __cli_GetTrustLevel ( enum __cli_TrustLevel * __param0 )
1> 
1>    {
1> 
1>      * __param0 = __cli_FullTrust ;
1> 
1>      return 0 ;
1> 
1>     
1> 
1>    }
1> 
1>   
1> 
1>  }
1>  </TokenStream>
1> 
1>  <TokenStream>
1> 
1>  namespace Platform
1> 
1>  {
1> 
1>    inline class Platform::Object ^ :: Platform :: IActivationFactory :: ActivateInstance ( )
1> 
1>    {
1> 
1>      class Platform::Object ^ __cli_returnValue ;
1> 
1>      long __hr = __cli_ActivateInstance ( & __cli_returnValue ) ;
1> 
1>      __cli_WinRTThrowError ( __hr ) ;
1> 
1>      return __cli_returnValue ;
1> 
1>     
1> 
1>    }
1> 
1>   
1> 
1>  }
1>  </TokenStream>
1> 
1>  <TokenStream>
1> 
1>  namespace CppWinRTComponentDll
1> 
1>  {
1> 
1>    inline long __stdcall :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: __cli_Platform_IActivationFactory____cli_ActivateInstance ( class Platform::Object ^* __cli_returnValue )
1> 
1>    {
1> 
1>      long __hr = 0 ;
1> 
1>      * __cli_returnValue = nullptr ;
1> 
1>      try
1> 
1>      {
1> 
1>        auto __tempValue = ActivateInstance ( ) ;
1> 
1>        * __cli_returnValue = __tempValue ;
1> 
1>       
1> 
1>      }
1> 
1>      catch ( :: Platform :: Exception ^ __param0 )
1> 
1>      {
1> 
1>        __hr = __param0 -> HResult ;
1> 
1>       
1> 
1>      }
1> 
1>      catch ( … )
1> 
1>      {
1> 
1>        __hr = -2147467259 ;
1> 
1>       
1> 
1>      }
1> 
1>      return __hr ;
1> 
1>     
1> 
1>    }
1> 
1>   
1> 
1>  }
1>  </TokenStream>
1> 
1>  <TokenStream>
1> 
1>  namespace CppWinRTComponentDll
1> 
1>  {
1> 
1>    long :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: __cli_QueryInterface ( class Platform::Guid % __param0 , void ** __param1 )
1> 
1>    {
1> 
1>      if ( __param0 . Equals ( __uuidof ( __cli_IUnknown ) ) || __param0 . Equals ( __uuidof ( __cli_IInspectable ) ) || __param0 . Equals ( __uuidof ( struct Platform::IActivationFactory ^ ) ) )
1> 
1>      {
1> 
1>        * __param1 = reinterpret_cast < void * > ( static_cast < struct Platform::IActivationFactory ^ > ( this ) ) ;
1> 
1>        __cli_refcount . Increment ( ) ;
1> 
1>        return 0 ;
1> 
1>       
1> 
1>      }
1> 
1>      return -2147467262 ;
1> 
1>     
1> 
1>    }
1> 
1>    unsigned long :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: __cli_AddRef ( )
1> 
1>    {
1> 
1>      long __cli_returnValue = __cli_refcount . Increment ( ) ;
1> 
1>      return ( unsigned long ) __cli_returnValue ;
1> 
1>     
1> 
1>    }
1> 
1>    unsigned long :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: __cli_Release ( )
1> 
1>    {
1> 
1>      long __cli_returnValue = __cli_refcount . Decrement ( ) ;
1> 
1>      if ( ! __cli_returnValue )
1> 
1>      {
1> 
1>        delete this ;
1> 
1>        :: Platform :: Heap :: Free ( reinterpret_cast < void * > ( this ) ) ;
1> 
1>       
1> 
1>      }
1> 
1>      return ( unsigned long ) __cli_returnValue ;
1> 
1>     
1> 
1>    }
1> 
1>    long :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: __cli_GetIids ( unsigned long * __param0 , class Platform::Guid ** __param1 )
1> 
1>    {
1> 
1>      struct __s_GUID __interfaceList [ ] =
1> 
1>      {
1> 
1>       
1> 
1>        {
1> 
1>          53 , 0 , 0 , 192 , 0 , 0 , 0 , 0 , 0 , 0 , 70
1> 
1>        }
1> 
1>       
1> 
1>      } ;
1> 
1>     
1> 
1>      return __winRT :: __winRTRuntime . __getIids ( 1 , __param0 , __interfaceList , __param1 ) ;
1> 
1>     
1> 
1>    }
1> 
1>    long :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: __cli_GetRuntimeClassName ( struct __cli_HSTRING__ ** __param0 )
1> 
1>    {
1> 
1>      return __winRT :: __winRTRuntime . __windowsCreateString ( ( const wchar_t * ) L"CppWinRTComponentDll.__CalculatorSampleActivationFactory" , 56 , __param0 ) ;
1> 
1>     
1> 
1>    }
1> 
1>    long :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: __cli_GetTrustLevel ( enum __cli_TrustLevel * __param0 )
1> 
1>    {
1> 
1>      * __param0 = __cli_FullTrust ;
1> 
1>      return 0 ;
1> 
1>     
1> 
1>    }
1> 
1>   
1> 
1>  }
1>  </TokenStream>
1> 
1>  <TokenStream>
1> 
1>  namespace CppWinRTComponentDll
1> 
1>  {
1> 
1>    class Platform::Object ^ :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: ActivateInstance ( )
1> 
1>    {
1> 
1>      return gcnew class CppWinRTComponentDll::CalculatorSample ( ) ;
1> 
1>     
1> 
1>    }
1> 
1>   
1> 
1>  }
1>  </TokenStream>
1> 
1>  <TokenStream>
1> 
1>  namespace CppWinRTComponentDll
1> 
1>  {
1> 
1>    long __stdcall :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: CreateFactory ( unsigned int * , struct __cli___classObjectEntry * , class Platform::Guid % __param2 , struct __cli_IUnknown ** __param3 )
1> 
1>    {
1> 
1>      class CppWinRTComponentDll::__CalculatorSampleActivationFactory ^ __pActivationFactory = gcnew :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory ( ) ;
1> 
1>      return __pActivationFactory -> __cli_QueryInterface ( __param2 , reinterpret_cast < void ** > ( __param3 ) ) ;
1> 
1>     
1> 
1>    }
1> 
1>    const wchar_t * __stdcall :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: GetTargetClassName ( )
1> 
1>    {
1> 
1>      return L"CppWinRTComponentDll.CalculatorSample" ;
1> 
1>     
1> 
1>    }
1> 
1>   
1> 
1>  }
1>  </TokenStream>
1> 
1>  <TokenStream>
1> 
1>  namespace CppWinRTComponentDll
1> 
1>  {
1> 
1>    const struct __cli___classObjectEntry __CalculatorSampleActivationFactory_Registration =
1> 
1>    {
1> 
1>      :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: CreateFactory , :: CppWinRTComponentDll :: __CalculatorSampleActivationFactory :: GetTargetClassName , nullptr , & __cli_no_factory_cache , nullptr
1> 
1>    } ;
1> 
1>   
1> 
1>    extern "C" __declspec ( allocate ( "minATL$__r" ) ) __declspec ( selectany ) const :: __cli___classObjectEntry * const CppWinRTComponentDll___CalculatorSampleActivationFactory__Entry = & __CalculatorSampleActivationFactory_Registration ;
1> 
1>   
1> 
1>  }
1>  </TokenStream>
1> 
========== Build: 1 succeeded, 0 failed, 0 up-to-date, 0 skipped ==========

 

The complete code of MainPage.xaml.cpp is as follows.

Code Snippet

//
// MainPage.xaml.cpp
// Implementation of the MainPage.xaml class.
//

#include "pch.h"
#include "MainPage.xaml.h"

using namespace Windows::UI::Xaml;
using namespace Windows::UI::Xaml::Controls;
using namespace Windows::UI::Xaml::Data;
using namespace CPPApplication1;

using namespace CppWinRTComponentDll;

MainPage::MainPage()
{
    InitializeComponent();

    CalculatorSample^ calcobj = ref new  CalculatorSample();
    //txtAddResult->Text = calcobj->Add(10,20).ToString();

    //// declare a stack variable to hold the value of the result
    int result;
    //call into  calc object low level __cli_Add() but no intellisense in this preview
    //HRESULT hr = calcobj->__cli_Add(10,20,&result);

    //create a c function that actually represent an ABI call we will be making
    //to add function which takes this pointer, 2 input parameters and an out parameter.
    typedef HRESULT (__stdcall* AddFunc_t) (CalculatorSample^ calc, int i, int j, int * result);
    //now we can take the calculator^ object, which is a pointer to a pointer to a vtable
    //and reinterpret cast it so that it can say ok now i have a pointer of  virtual function
    //which are vtables and i am going to specifically pick the sixth function of that and call into it.
    //reinterpret_cast takes the calcobj ^ and cast it to a pointer to a pointer
    AddFunc_t* addFunc = *reinterpret_cast<AddFunc_t**>(calcobj);
    addFunc[6](calcobj,10,20, &result);

    ////CalculatorSample^ calcobj = ref new CalculatorSample();
    ////int* vtable_array = (int*)calcobj;
    ////int* icalc_vtable = (int*)vtable_array[0];
    ////int* compute_will_be_fptr = (int*)icalc_vtable[6];
    ////typedef HRESULT (__stdcall *compute_fptr_t)(CalculatorSample^, int, int, int*);
    ////compute_fptr_t compute_fptr = (compute_fptr_t)compute_will_be_fptr;
    ////compute_fptr(calcobj,10,20, &result);

    txtAddResult->Text = result.ToString();
}

MainPage::~MainPage()
{
}

 

Download the source code from here.

"If you limit your choices only to what seems possible or reasonable, you disconnect yourself from what you truly want, and all that is left is a compromise."

WinRT from the eyes of a .NET developer

Following is the compilation of information related to what the .NET developer need to know about WinRT.

This biggest confusion, has been around the use of the .NET Framework across the blue side and green side. The reason for the, as I call it, .NET Metro Profile is because the Metro style apps run in an app container that limits what the application can have access to in order to protect the end user from potentially malicious apps. As such, the Metro Profile is a subset of the .NET Client Profile and simply takes away some of the capabilities that aren’t allowed by the app container for Metro style apps. Developers used to .NET will find accessing the WinRT APIs very intuitive – it works similarly to having an assembly reference and accessing the members of said referenced assembly.

At the lowest level, WinRT is an object model defined on ABI level. It uses COM as a base (so every WinRT object implements IUnknown and does refcounting), and builds from there. It does add quite a lot of new concepts in comparison to COM of old, most of which come directly from .NET – for example, WinRT object model has delegates, and events are done .NET-style (with delegates and add/remove subscriber methods, one per event) rather than the old COM model of event sources and sinks. Of other notable things, WinRT also has parametrized (“generic”) interfaces.

One other big change is that all WinRT components have metadata available for them, just like .NET assemblies. In COM you kinda sorta had that with typelibs, but not every COM component had them. For WinRT, the metadata is contained in .winmd files – look inside “C:\Program Files (x86)\Windows Kits\8.0\Windows Metadata\” in Developer Preview. If you poke around, you’ll see that they are actually CLI assemblies with no code, just metadata tables. You can open them with ILDASM, in fact. Note, this doesn’t mean that WinRT itself is managed – it simply reuses the file format.

Then there are a number of libraries implemented in terms of that object model – defining WinRT interfaces and classes. Again, look at “Windows Metadata” folder mentioned above to see what’s there; or just fire up Object Browser in VS and select “Windows 8.0″ in the framework selector, to see what’s covered. There’s a lot there, and it doesn’t deal with UI alone – you also get namespaces such as Windows.Data.Json, or Windows.Graphics.Printing, or Windows.Networking.Sockets.

Then you get several libraries, which are specifically dealing with UI – mostly these would be various namespaces under Windows.UI or Windows.UI.Xaml. A lot of them are very similar to WPF/Silverlight namespaces – e.g. Windows.UI.Xaml.Controls is closely matching System.Windows.Controls; ditto for Windows.UI.Xaml.Documents etc.

Now, .NET has the ability to directly reference WinRT components as if they were .NET assemblies. This works differently from COM Interop – you don’t need any intermediate artifacts such as interop assemblies, you just /r a .winmd file, and all types and their members in its metadata become visible to you as if they were .NET objects. Note that WinRT libraries themselves are fully native (and so native C++ programs that use WinRT do not require CLR at all) – the magic to expose all that stuff as managed is inside the CLR itself, and is fairly low level. If you ildasm a .NET program that references a .winmd, you’ll see that it actually looks like an extern assembly reference – there’s no sleight of hand trickery such as type embedding there.

It’s not a blunt mapping, either – CLR tries to adapt WinRT types to their equivalents, where possible. So e.g. GUIDs, dates and URIs become System.Guid, System.DateTime and System.Uri, respectively; WinRT collection interfaces such as IIterable<T> and IVector<T> become IEnumerable<T> and IList<T>; and so on. This goes both ways – if you have a .NET object that implements IEnumerable<T>, and pass it back to WinRT, it’ll see it as IIterable<T>.

Ultimately, what this means is that your .NET Metro apps get access to a subset of the existing standard .NET libraries, and also to (native) WinRT libraries, some of which – particularly Windows.UI – look very similar to Silverlight, API-wise. You still have XAML to define your UI, and you still deal with the same basic concepts as in Silverlight – data bindings, resources, styles, templates etc. In many cases, it is possible to port a Silverlight app simply by using the new namespaces, and tweaking a few places in code where the API was adjusted.

WinRT itself doesn’t have anything to do with HTML and CSS, and it bears relation to JavaScript only in a sense that it is also exposed there, similar to how it is done for .NET. You don’t need to deal with HTML/CSS/JS when you use WinRT UI libraries in your .NET Metro app (well, I guess, if you really want to, you can host a WebView control…). All your .NET and Silverlight skills remain very much relevant in this programming model.

Under the hood Part 5 : JavaScript application & C++ WinRT Component DLL – WinRT, Windows 8, C++, Metro

JavaScript application calling WinRT Component DLL

In this part, we will create a C++ WinRT Component DLL and access it from a JavaScript application.

We have developed a C++ WinRT Component DLL & C#.NET application in the post here Under the hood Part 1 : C++ WinRT Component DLL & C#.NET Metro application

we have seen the compiler generated components for making the C# application access the C++ WinRT component here Under the hood Part 2 : C++ WinRT Component DLL & C#.NET Metro application

We have seen the packaging and installation process that happens in the background during building and deploying of the applications here Under the hood Part 3 : WinRT, Windows 8, C++, C#.NET, Metro, WinRT Component DLL

We have seen the C++ XAML application calling the C++ WinRT Component DLL here Under the hood Part 4 : C++ WinRT Component DLL & C++ XAML application – WinRT, Windows 8, C++, Metro

Generally, in a LOB application, we might have to build a C++ Component DLL to take advantage of the performance of C++ in complex or computationally-intensive operations. The C++ component can access Windows operating system services that are not accessible through the Windows Runtime in the current version. Mostly, to reuse existing code that is already written and tested.

Download the source code here.

Step 1:

Create a Windows Runtime C++ Component DLL:

Open Visual Studio 2011 –> File –> New Project –> Go to Installed Templates section –> Visual C++ –>Select WinRT Component DLL and name it as CPPWinRTComponentDll as shown in the following figure.

Fig 1: CPPWinRTComponentDll project

Open WinRTComponent.h file and create an Employee class as shown in the following code snippet. The Platform namespace is where C++ defines its classes that are specific Windows Runtime types.

Create a private variables address_ and employeeid_. These are used as backing store to hold the values. We will use get() & set() properties to set or get these values.

    private:
            // Backing store for property address_ & employeeid_.
            Platform::String^ address_;
            int employeeid_;

 

In the public section, add the following code which are properties for the above backing store.

        property Platform::String^ Address
        {
            Platform::String^ get()
            {
                return  (address_);
            }
        }

        // Property with custom setter/getter
        property int EmployeeId
        {
            int get()
            {
                return employeeid_;
            }

            //    ‘set’ accessor is missing its value parameter
            void set(int value)
            {
                if(value <= 0)
                {
                    throw ref new Platform::InvalidArgumentException();
                    employeeid_ = value;
                }
            }
        }

 

We can also add some trivial get/set property with the compiler generating the backing store.

    public:
        // Trivial get/set property with compiler-generated backing store.
        property Platform::String^ Name;

 

Following is the complete code of the Employee class.

Code Snippet

public ref class Employee sealed
    {
    private:
            Platform::String^ address_;
            int employeeid_;
           
            //If i use a stack syntax, i get compilation error
            //Platform::String address2_;
            //Error    1    error C3149: ‘Platform::String’ : cannot use this type here without a top-level ‘^’   
            //c:\projects\cppwinrtcomponentdll with cpp app string\cppwinrtcomponentdll\winrtcomponent.h   

    public:

        property Platform::String^ Name;
        property Platform::String^ Address
        {
            Platform::String^ get()
            {
                return  (address_);
            }
        }

        property int EmployeeId
        {
            int get()
            {
                return employeeid_;
            }

            //    ‘set’ accessor is missing its value parameter
            void set(int value)
            {
                if(value <= 0)
                {
                    throw ref new Platform::InvalidArgumentException();
                    employeeid_ = value;
                }
            }
        }

    public:
        Platform::String^ SayHello()
        {
            return "Hello World";
        }

    public:
        int Add(int x, int y)
        {
            return x+y;
        }

    };

 

When you code your C++ component, if needed, you can use the regular C++ library and built-in types inside the class code except at the abstract binary interface (ABI) boundary where you are passing data to and from JavaScript. There, use Windows Runtime types and the special syntax that Visual C++ supports for creating and manipulating those types.

You have to make the Employee class as activatable class so that it can instantiated from another language such as JavaScript. To be consumable from another language such as JavaScript, a component must contain at least one activatable class. If needed, a Windows Runtime component can contain multiple activatable classes as well as additional classes known only internally to the component. Client code creates an instance of the component by using the new keyword just as for any class.

The Employee class must be declared as public ref class sealed. The ref class keywords tell the compiler to create the class as a Windows Runtime compatible type, and the sealed keyword specifies that the class cannot be inherited. A class must be sealed to be consumed by JavaScript.

In the Platform::String^ address_, the ^ operator signifies a handle to a Windows Runtime string type that under the covers is reference-counted and deleted when the count reaches zero. Instances of these types are created by using the ref new keywords. Do not explicitly call delete on these instances.

Types must be passed to and from the public methods as Windows Runtime types. If you use the C++ built-in types such as int, double and so on, the compiler will automatically convert them to the appropriate Windows Runtime type. No such conversion occurs unless you are passing the type across the ABI. Complex types such as Platform::String^ must be specified explicitly.

Step 2:

Creating a JavaScript Windows Metro style Application project:

To create a project in this solution, right-click the solution node in Solution Explorer. and select Add Project > Blank Application. Name it as WinWebApp1.

Fig 2: creating the JavaScript project

Add a reference to the component project

After you have compiled the C++ project for the first time, you can add it as a project reference in the JavaScript project. Right-click the References node in the JavaScript project, and select Add. When the Add References Manager dialog box appears, click “Solution” to display the available references in the solution. Select  “CPPWinRTComponentDll ” in this solution and click on Add button as shown in figure 3; The namespace and all public types and methods are now available to your JavaScript code. You can verify this by experimenting with the Member List or Statement Completion feature in the JavaScript file.

Fig 3: Adding reference to the C++ WinRT Component DLL.

Add the HTML markup that invokes JavaScript.

Add the following HTML into the <body> node of the default.html page

<body>
    <button id="callwinrt" onclick="CallWinRT()">Call WinRT</button>
<p></p>
    <label id ="Label1" style="background-color: grey;">Activation Object Result ->  </label><label id ="loaded" style="background-color: #51B65A;"></label>
    <p></p>
     <label id ="Label2" style="background-color: grey;">Calling Employee::SayHello() method     </label><label id ="callmethod" style="background-color: #51B65A;"></label>
    <p></p>
     <label id ="Label3" style="background-color: grey;" >Getting  Employee.Name Property value    </label><label id ="retrievedproperty" style="background-color: #51B65A;"></label>
    <p></p>

</body>

 

The default.html page appears as following.

Code Snippet

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>WinWebApp1</title>
    <!– WinJS references –>
    <link rel="stylesheet" href="/winjs/css/ui-dark.css" />
    <script src="/winjs/js/base.js"></script>
    <script src="/winjs/js/wwaapp.js"></script>
    <!– WinWebApp1 references –>
    <link rel="stylesheet" href="/css/default.css" />
    <script src="/js/default.js"></script>
</head>
<body>
    <button id="callwinrt" onclick="CallWinRT()">Call WinRT</button>
<p></p>
    <label id ="Label1" style="background-color: grey;">Activation Object Result ->  </label><label id ="loaded" style="background-color: #51B65A;"></label>
    <p></p>
     <label id ="Label2" style="background-color: grey;">Calling Employee::SayHello() method     </label><label id ="callmethod" style="background-color: #51B65A;"></label>
    <p></p>
     <label id ="Label3" style="background-color: grey;" >Getting  Employee.Name Property value    </label><label id ="retrievedproperty" style="background-color: #51B65A;"></label>
    <p></p>

</body>
</html>

 

Add the JavaScript event handlers that call into the component DLL

Add the following function CallWinRT() at the end of the default.js file. This function is called when you click the button “Call WinRT” on the main page. Notice how JavaScript activates the C++ class, and then calls its methods and populates the HTML labels with the return values.

function CallWinRT() {
    // activate the native Windows Runtime component
    var nativeObject = new CppWinRTComponentDll.Employee();
    document.getElementById(‘loaded’).innerHTML = nativeObject;

    //call a method
    var num = nativeObject.sayHello();
    document.getElementById(‘callmethod’).innerHTML = num;

    nativeObject.name = "Kishore Babu";

    // get the value of the string property
    var propValue = nativeObject.name;
    document.getElementById(‘retrievedproperty’).innerHTML = propValue;
}

 

The complete code of default.js file is as follows.

Code Snippet

(function () {
    ‘use strict’;
    // Uncomment the following line to enable first chance exceptions.
    // Debug.enableFirstChanceException(true);

    WinJS.Application.onmainwindowactivated = function (e) {
        if (e.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) {
            // TODO: startup code here
        }
    }

    WinJS.Application.start();
})();

function CallWinRT() {
    // activate the native Windows Runtime component
    var nativeObject = new CppWinRTComponentDll.Employee();
    document.getElementById(‘loaded’).innerHTML = nativeObject;

    //call a method
    var num = nativeObject.sayHello();
    document.getElementById(‘callmethod’).innerHTML = num;

    nativeObject.name = "Kishore Babu";

    // get the value of the string property
    var propValue = nativeObject.name;
    document.getElementById(‘retrievedproperty’).innerHTML = propValue;
}

 

Build the solution & deploy the application. If you go to start window, you will find an application WinWebApp1. Click on it.

Click on call WinRT button. The values from the C++ DLL are returned and set in the JavaScript application as shown in the following figure.

When you build a solution that contains a JavaScript project and a Windows Runtime Component DLL project, the JavaScript project files and the compiled DLL are merged into one package, which you can then deploy locally or remotely for testing or submit to the Windows Store. You can also distribute just the component project as an Extension SDK.

Debugging: When you debug a JavaScript solution that has a component DLL, you can set the debugger to enable either stepping through script, or stepping through native code in the component, but not both at the same time. To change the setting, right-click the JavaScript project node in Solution Explorer, then select Properties > Debugging > Debugger Type.

Be sure to select appropriate capabilities in the package designer. For example, if you are attempting to open a file using the Windows Runtime APIs, be sure to select the Document Library Access checkbox in the Capabilities pane of the package designer.

Download the source code here.

As a C++ developer, I find this useful. If you are a C++ developer and new to JavaScript, you sometimes make the mistake of not using the camel-casing in JS. If your JavaScript code does not seem to be recognizing the public properties or methods in the component, make sure that in JavaScript you are using camel-casing. For example, the Platform::String^ SayHello() C++ method must be referenced as sayHello() in JavaScript.

"The task of the leader is to get his people from where they are to where they have not been." — Henry Kissinger

Under the hood Part 4 : C++ WinRT Component DLL & C++ XAML application – WinRT, Windows 8, C++, Metro

Calling WinRT Component from C++

We have developed a C++ WinRT Component DLL & C#.NET application in the post here Under the hood Part 1 : C++ WinRT Component DLL & C#.NET Metro application

we have seen the compiler generated components for making the C# application access the C++ WinRT component here Under the hood Part 2 : C++ WinRT Component DLL & C#.NET Metro application

We have seen the packaging and installation process that happens in the background during building and deploying of the applications here Under the hood Part 3 : WinRT, Windows 8, C++, C#.NET, Metro, WinRT Component DLL

Going further, I created a C++ Metro application and accessed the C++ WinRT Component DLL from this application. The interesting part here is that C++ applications is XAML based. No more .RC and resource.h files in C++ (for metro). In the previous post, we created a WinRT C++ DLL that contains a class calculatorSample. Now let us create  a C++ application to consume the C++ WinRT DLL.

To get started with creating a C++ XAML application, go to Visual Studio 2011 –> Solution Explorer–> New Project –> Go to Installed Templates section –> Visual C++ –>Select Application and name it as CPPApplication1 as shown in the following fig 1.

Fig 1: Creating a C++ XAML application.

Right click on the project, click on Add References and the following dialog shown in figure 2 comes up.

Fig 2: Reference manager dialog to add references to another components.

Click on Solution section –> Projects and Select  CppWinRTComponentDLL –> click on Add button and click on Close as shown in figure 3.

Fig 3: Selecting WinRT CppWinRTComponentDLL.

The CppWinRTComponentDLL reference appears in the References section as shown in the following figure 4.

Fig 4: CppWinRTComponentDLL dll appears in the References section.

Goto MainPage.xaml.cpp and include the namespace for CppWinRTComponentDLL

Code Snippet

using namespace CppWinRTComponentDll;

 

Then create an object of calculatorSample on the heap using ref new. In this scenario, ref new  is like cocreateinstance of COM. It’s a smart allocator. we also use ref class to indicate the authoring of a Windows Runtime class . using ^ to represent a “refcounted” pointer in ZW fits quite well

The following code shows how to use the ref new expression to create a new reference-counted Windows Runtime object. Note that you use the ^ (“hat”) symbol instead of the pointer dereference operator (*) when declaring the variable, but that you use the familiar -> operator to access the objects instance members. Note also that you do not call delete explicitly on the object. The object will be destroyed deterministically when the last remaining copy of it goes out of scope. At the lowest level, the object is basically a COM object owned by a smart pointer.

Code Snippet

CalculatorSample^ calcobj = ref new  CalculatorSample();
txtAddResult->Text = calcobj->Add(10,20).ToString();

 

So from the C++ application, we are calling the C++ Windows Runtime Component DLL. This is all native code. C++ calling C++ and everything is ref counted.

Compiler options: /ZW enable WinRT language extensions /AI<dir> add to assembly search path <dir> is the folder where the compiler searches the winmd files /FU<file> forced using assembly/module force the inclusion of the specified winmd file /D "WINAPI_FAMILY=2" set this define to compile against the ModernSDK subset of Win32

Linker options: /APPCONTAINER[:NO] marks the executable as runnable in the appcontainer (only) /WINMD[:{NO|ONLY}] emits a winmd; if “ONLY” is specified, does not emit the executable, but just the winmd /WINMDFILE:filename name of the winmd file to emit /WINMDDELAYSIGN[:NO] /WINMDKEYCONTAINER:name /WINMDKEYFILE:filename used to sign the winmd file

However, in a Metro style app or Windows Runtime component, all the C++ code is native. The /ZW compiler option causes the Component Extensions to be compiled for Windows Runtime. The /cli compiler option causes them to be compiled for C++/CLI. Currently, C++/CLI is not supported for Metro style apps

Code snippet of the complete MainPage class.

Code Snippet

//
// MainPage.xaml.cpp
// Implementation of the MainPage.xaml class.
//

#include "pch.h"
#include "MainPage.xaml.h"

using namespace Windows::UI::Xaml;
using namespace Windows::UI::Xaml::Controls;
using namespace Windows::UI::Xaml::Data;
using namespace CPPApplication1;

using namespace CppWinRTComponentDll;

MainPage::MainPage()
{
    InitializeComponent();

      CalculatorSample^ calcobj = ref newCalculatorSample();
    txtAddResult->Text = calcobj->Add(10,20).ToString();

    int result;
    HRESULT hr = calcobj->__cli_Add(20,30,&result);
    txtAddResult->Text = result.ToString();
}

MainPage::~MainPage()
{
}

All Windows Runtime types derive from the universal base class Platform::Object. There is therefore an implicit conversion from any Windows Runtime object to Platform::Object.

Code snippet of the XAML page.

Code Snippet

<UserControl x:Class="CPPApplication1.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation&quot;
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml&quot;
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008&quot;
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006&quot;
    mc:Ignorable="d"
    d:DesignHeight="768" d:DesignWidth="1366">
    
    <Grid x:Name="LayoutRoot" Background="#FF0C0C0C">
        <TextBox x:Name="txtAddResult" HorizontalAlignment="Left" Text="TextBox" VerticalAlignment="Top" Margin="343,90,0,0" Width="212"/>
        <TextBlock HorizontalAlignment="Left" TextWrapping="Wrap" Text="Calling C++ component Add method from C++ XAML Application" VerticalAlignment="Top" Margin="81,90,0,0" Height="45" Width="258" FontSize="14" FontWeight="Bold"/>

    </Grid>
    
</UserControl>

 

Build the solution and deploy the application. The application output is as follows.

Configuration settings:

Enable Windows Runtime Extensions enables the runtime extensions throughout the type system which includes the ability to do Boxing. I.e. Boxing to WinRT type system. Every fundamental types and WinRT types are derived from Platform.Object.

heap-allocated objects with heap semantics:

Calculator^ calc = ref new Calculator(); // Calculator is a ref class from a custom WinRT component

txtResult->Text = calc->Add(10, 20).ToString();

The ^syntax will fire a destructor when the refcount on the object drops to 0, or if you explicitly call delete. (So if you handed the object out it’s not necessarily at the end of your scope)

heap-allocated objects with Stack semantics:

Calculator calc;

txtResult->Text = calc.Add(10, 20).ToString();

Both of those create heap-allocated objects behind the scenes, but the difference is whether you logically have heap semantics vs. stack semantics.

The stack syntax will fire a destructor when the object goes out of scope (or on an exception etc.). This is important when you e.g. handed of the object to another thread or async callback, so there may still be a refcount on it, but you need to get rid of it right away. (E.g. a file handle that needs to be closed otherwise the file is locked). The main advantage is exception-safe deterministic destruction.

PS: Because of the nature of refcounting, it’s a little bit less important with WinRT to have deterministic destruction than with e.g. the /clr and a garbage collected heap (where the point of destruction is virtually random). However, you will find that with async patterns it is common to get into a situation where you’re transfer the ownership of an object from one thread to another (e.g. via a lambda). There is then a race condition between the two threads for releasing the object. This is generally still ok, but if the object represents a file or other exclusive resource it might be critical to perform the destruction at a specific time, rather than relying on the timing between the two threads.

value classes & Ref classes

Int32 x(15); // Compiles and x is initialized and works as expected.

String str("test1"); // Doesn’t compile and compiler complains C3149: ‘Platform::String’ : cannot use this type here without a top-level ‘^’

Int32 is a value class, and String or the custom winRT component are all ref class. They are different.

Differences between C++/CLI and WinRT C++

In terms of the differences like flags are as follows.

Basic types:
/clr: From mscorlib.dll (System::* types)
/ZW: From vccorlib.dll (Platform::* types)

Lifetime management:
/clr: Garbage collected
/ZW: Refcounted

Cycles Broken:
/clr: By garbage collector
/ZW: Broken by user (weak references or explicit delete)

Code generation:
/clr: MSIL + native code. Can create a cross-platform binary if MSIL-only.
/ZW: Native code only. Binaries target a specific platform.

Object Creation:
/clr: gcnew
/ZW: ref new

interior_ptr:
/clr: Supported
/ZW: Not supported

pin_ptr:
/clr: Supported
/ZW: Not supported

V% (% when it refers to a byref (kind’a like an "interior_ref") ):
/clr: Supported
/ZW: Not supported

R% (% when it refers to an implicitly dereferenced ref type):
/clr: Supported
/ZW: Supported

Ref to ^:
/clr: R^%
/ZW: R^&

Boxing:
/clr: syntax V^
/ZW: IReference<V>^

Dereferenced box type:
/clr: V%
/ZW: const V

Generics:
/clr: Generics classes, interfaces & delegates allowed.
/ZW: Generic interfaces & delegates only.

Static constructors:
/clr: Supported
/ZW: Not supported

Address of member of ref class:
/clr: Returns an interior_ptr
/ZW: Returns a type*

friends:
/clr: Not supported
/ZW: Supported

C++ class embedded in ref class:
/clr: Not supported
/ZW: Supported

ref class embedded in C++ class:
/clr: Not supported
/ZW: Supported (R-on-stack)

^ embedded in C++ class:
/clr: Not supported (Needs GCHandle)
/ZW: Supported

^ embedded in value class with value class on native heap:
/clr: Not supported
/ZW: Supported (for String^)

Global ^:
/clr: Not supported
/ZW: Supported

Global R-on-stack:
/clr: Not supported
/ZW: Supported

Finalizer:
/clr: Supported
/ZW: Not supported

Destructor:
/ZW: Runs on IDisposable::Dispose (delete / stack unwind) only
/clr: Runs on IDisposable::Dispose (delete / stack unwind) -or- last release (never both)

T::typeid:
/clr: Supported
/ZW: Not supported

R-on-stack (ref class on stack) syntax is supported on C++/cli and C++/CX, but you’ll notice that unfortunately the /CX implementation in the developer preview release has a code generation bug that will make it impractical to test this right now. (R^ and R% should be fine though). The most important reason for R-on-stack is exception-safe destruction (Like ‘using’ gives you in C#) – other than that it is purely compiler syntactic sugar.

Download the source code here.

"If one advances confidently in the direction of his dreams, and endeavors to live the life which he has imagined, he will meet with success unexpected in common hours." — Henry David Thoreau

Under the hood Part 3 : Internals of how the application is installed and run – WinRT, Windows 8, C++, C#.NET, Metro

Under the hood Part 3 : WinRT, Windows 8, C++, C#.NET, Metro, WinRT Component DLL

We have developed a C++ WinRT Component DLL & C#.NET application in the post here Under the hood Part 1 : C++ WinRT Component DLL & C#.NET Metro application

we have seen the compiler generated components for making the C# application access the C++ WinRT component here Under the hood Part 2 : C++ WinRT Component DLL & C#.NET Metro application

See the post on First Look at What’s New in Windows 8 here.

Going further, I created a C++ Metro application and accessed the C++ WinRT Component DLL from this application. The interesting part here is that C++ applications is XAML based. No more .RC and resource.h files in C++ (for metro). We will explore the C++ application in another post. In this post, let us walk through the packaging and installation process that happens in the background during building and deploying of the applications.

Basically, there are two registrations for our application.

1. Extension registration
2. Class registration.

The figure 1 (from Build con) shows the relation between the two.

Fig : Slide related to Extension Catalog and Class Catalog shown @ Build con.

Go to  Visual Studio 2011 –> Solution Explorer –> CSharpApplication project, here you can find a file named Package.appxmanifest as shown in figure 1 . This file has most of the information needed to deploy the application. This is the information that windows uses to identify the application. Package Name is the name used in most of the identification process.

Fig 1: Package.appxmanifest file in Visual Studio 2011 Solution Explorer.

Code snippet of Package.appxmanifest file.

Code Snippet

<?xml version="1.0" encoding="utf-8"?>
<Package xmlns="http://schemas.microsoft.com/appx/2010/manifest">
  <Identity Name="CSharpApplicationCallingCPPComponent" Publisher="CN=Kishore" Version="1.0.0.0" />
  <Properties>
    <DisplayName>CSharpApplication</DisplayName>
    <PublisherDisplayName>Kishore</PublisherDisplayName>
    <Logo>Images\StoreLogo.png</Logo>
    <Description>CSharpApplication</Description>
  </Properties>
  <Prerequisites>
    <OSMinVersion>6.2</OSMinVersion>
    <OSMaxVersionTested>6.2</OSMaxVersionTested>
  </Prerequisites>
  <Resources>
    <Resource Language="en-us" />
  </Resources>
  <Applications>
    <Application Id="App" Executable="csharpapplication.exe" EntryPoint="CSharpApplication.App">
      <VisualElements DisplayName="CSharpApplication" Logo="Images\Logo.png" SmallLogo="Images\SmallLogo.png" Description="CSharpApplication" ForegroundText="light" BackgroundColor="#222222" InitialRotationPreference="portrait">
        <SplashScreen Image="Images\SplashScreen.png" />
      </VisualElements>
    </Application>
  </Applications>
  <Capabilities>
    <Capability Name="internetClient" />
  </Capabilities>
</Package>

 

The applications implement contract like search contract, share, play queue contract. Those contract registrations are the extensions registration for the operating system.  Tile that you see in the Windows start page is just another contract activation. I,e windows.launch contract. So if you go to HKEY_CURRENT_USER\Software\Classes\Extensions\ContractId\Windows.Launch, you can find your application package id that we saw in figure 1. Everything under Windows.Launch is organized by package ID as shown in the figure 2 below.

Fig 2: Registry settings showing the registered Extensions.

From figure 2, we can see our package HKEY_CURRENT_USER\Software\Classes\Extensions\ContractId\Windows.Launch\ PackageId\csharpapplicationcallingcppcomponent_1.0.0.0_x86_neutral_kb63pw67p0swp. This package has a  ActivatableClassId key . Under that we see App as shown in figure 3. This is the class registration for this extension.

Fig 3: App registry settings for your application.

Let us see how the class registration for the applications looks like. First, We have extensions which say I implement this contract for ex I implement this launch and then we have classes. The extensions point to the classes. classes are actually the implementation. All applications are just Windows Runtime objects to the Windows OS, this is where all it starts. This is the windows runtime class that the OS knows about for your application.

The interesting part is in the class registration for the application. If we go up in the registry editor, we should see a registry key called ActivatableClasses at  HKEY_CURRENT_USER\Software\Classes\ActivatableClasses, this is where the class registrations are for all of our applications are. Here again we find package. All extensions, all classes are organized based on the package. That means our application or package has unique set of classes and they don’t share extension points or classes with other applications. They are all unique for our app. If we expand it, we see ActivatableClassId, the same name we saw in extensions. Here we should find the App classId. This is the WinRT class registration. This is the same for all types of applications, libraries etc.

Here we can see some registration attributes . The ActivationType is an important one. Windows Runtime supports two activation styles.

1. InProcess activation
2. Out of process activation

So Windows Runtime supports InProcess activation where we provide the DLL and windows load that into the process and it also supports out of process activation, where we will provide an exe and windows will launch the exe as your class implementation.

Registry key values:

ActivationType = 1 indicates its out of process activation class. out of process classes have a server. we have to know where the executable is, so there is a server registion here.

ActivationType = 0 indicates its in process activation

Out of process has a server and so there is a server registration here. Server with value App.AppXpdnr4x0evrk1yjmz5xfw2ksncfcjc5er.mca as shown in figure 4.

Fig 4: Server registry values for your application.

In figure 3, below the ActivationType , we can find Server attribute and it contains the App.AppXpdnr4x0evrk1yjmz5xfw2ksncfcjc5er.mca we got from the above Server value.  The server registration, tells the windows runtime enough information about what code we actually need to get from the disk and start running to get the app up and running. The ExePath attribute gives the path to the exe.

Windows runtime supports two apartment models. MTA & STA. If you have worked in VC++ COM, COM+ earlier, then you might have programmed the components for Multi Threaded Apartment model & Single Threaded Apartment model.

Let us see some more ActivatableClassId entries for Windows Runtime present at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsRuntime as shown in figure 5.

Fig 5: Windows Runtime classes information.

Finally, the slide that caught my attention was the deployment pipeline process shown in Fig 6 that shows the overall view of the above mentioned information.

Figure 6 showing the role of the deployment engine @ Build Con.

"Only those who risk going too far can possibly find out how far they can go." – T.S. Eliot

Under the hood Part 2 : C++ WinRT Component DLL & C#.NET Metro application

We have developed a C++ WinRT Component DLL & C#.NET application in the post here Under the hood Part 1 : C++ WinRT Component DLL & C#.NET Metro application

The important point here is that the  C# application is accessing the C++ WinRT component through RCW mechanism. The same application can be developed with JavaScript also that can use the C++ DLL that we developed. Wow, cool right? 

To understand the simplicity of the new programming model, we created a C++ WinRT Component DLL in part 1, which is all the code you need to author a Windows Runtime component.

Please download the code and extract the files.

Code Snippet

#pragma once

using namespace Windows::Foundation;

namespace CppWinRTComponentDll
{

    public ref class CalculatorSample sealed
    {
    public:
        int Add(int x, int y);
        int Sub(int x, int y);
        int Mul(int x, int y);

    };
}

In this example, you will immediately notice some keywords that are not part of standard C++. Visual C++ defines a few Component Extensions that, in a Metro style app, are essentially syntactic sugar over the underlying COM calls involved in creating and consuming Windows Runtime types. You typically use these extensions in the public interfaces where your code is passing Windows Runtime types back and forth across the ABI to JavaScript, C#, or Visual Basic (or even another C++ module). Visual C++ provides a variety of implicit conversions between Windows Runtime types and standard C++ types. The typical pattern is to use standard C++ types and libraries internally as usual, and convert to Windows Runtime types in the public interfaces.

So how did the C++ component get pulled into .net application? When we build the CppWinRTComponentDll project, we see the following in the output window. Notice the highlighted CppWinRTComponentDll.winmd text. This means the compiler is generating a file of type windmd.

1>—— Build started: Project: CppWinRTComponentDll, Configuration: Debug Win32 ——
1>  CppWinRTComponentDll.vcxproj -> C:\Users\Kishore\Documents\Visual Studio 11\Projects\CppWinRTComponentDll With CSharp App\Debug\CppWinRTComponentDll\CppWinRTComponentDll.winmd
1>  LINK : C:\Users\kishore\Documents\Visual Studio 11\Projects\CppWinRTComponentDll With CSharp App\Debug\CppWinRTComponentDll\CppWinRTComponentDll.dll not found or not built by the last incremental link; performing full link
1>     Creating library C:\Users\kishore\Documents\Visual Studio 11\Projects\CppWinRTComponentDll With CSharp App\Debug\CppWinRTComponentDll\CppWinRTComponentDll.lib and object C:\Users\kishore\Documents\Visual Studio 11\Projects\CppWinRTComponentDll With CSharp App\Debug\CppWinRTComponentDll\CppWinRTComponentDll.exp
1>  CppWinRTComponentDll.vcxproj -> C:\Users\kishore\Documents\Visual Studio 11\Projects\CppWinRTComponentDll With CSharp App\Debug\CppWinRTComponentDll\CppWinRTComponentDll.dll
========== Build: 1 succeeded, 0 failed, 0 up-to-date, 0 skipped ==========

You can notice the CppWinRTComponentDll.winmd file in the debug folder (CppWinRTComponentDll With CSharp App\Debug\CppWinRTComponentDll) as shown in Figure 1.

Fig 1: .WinMD File present in CppWinRTComponentDll folder inside the Debug folder.

This WinMD file is essentially a CLI meta data file and can be opened in ILDASM as shown in figure 2. CppWinRTComponentDll is exposed using API metadata present in CppWinRTComponentDll.winmd file. The format of WinMD file is Ecma-335 and this is the same format used by the .NET framework. It just used the ECMA-335 file format standard & the framework and nothing more than that. The underlying binary contract makes it easy for us to access the CppWinRTComponentDll APIs directly in the development language of our choice. The shape and structure of the CppWinRTComponentDll APIs can be understood by both static languages such as C# and dynamic languages such as JavaScript. IntelliSense is available in JavaScript, C#, Visual Basic, and C++ as you can see in the C# application (CSharpApplication project).

Fig 2: Opening CppWinRTComponentDll.winmd file using ILDASM.

This CppWinRTComponentDll.winmd file is created by c++ compiler and this can be seen as a cross language header file because c# cannot understand c++ header and neither JavaScript. so we need to have the file format that all languages understand and that is the .winmd file format. Although we authored a CalculatorSample class, what the compiler did for us is that, it also created a interface __ICalculatorSamplePublicNonVirtuals as shown in figure 3, which is the com interface used to talk to the calculator class. This adds it to the public surface.

Fig 3: Interface ICalculatorSamplePublicNonVirtuals created by the compiler

Manifest of the CppWinRTComponentDll.winmd file can be seen in figure 4.

Fig 4: Manifest of the CppWinRTComponentDll.WinMD File. Note the first entry, mscorlib.

we can see the Add method signature stored in the WinmD file in figure 5.

Figure 5: Add method signature present in CppWinRTComponentDll.winmd file.

Code Snippet

.method public newslot abstract virtual instance int32
Add(int32 x,
int32 y) cil managed
{
} // end of method __ICalculatorSamplePublicNonVirtuals::Add

 

In the ILDASM, click on the .class interface private abstract auto ansi windowsruntime. The GUID attribute. this is like specifying the GUID of the interface as shown in figure 6. This is the GUID for the component.

Fig 6: GUID of the interface.

The WinMD file does not contain any IL. This is just like a header information so that other languages can understand. This makes the Projections to happen. The calculator is a ref class itself. The CppWinRTComponentDll.CalculatorSample class implements from .__ICalculatorSamplePublicNonVirtuals and it implements Add,Sub and Mul methods as shown in the following figure 7.

Fig 7: CppWinRTComponentDll.CalculatorSample class implements from __ICalculatorSamplePublicNonVirtuals Interface.

Note that every object inside WinRT is ref counted.

Details about the C++ WinRT Component DLL created in part 1 (MSDN): C++/CX (Component Extensions)

Visual C++ in Visual Studio 11 for has a new programming model for creating Metro style apps and components. One of the primary features of the new model is the abstract binary interface, or ABI, which defines an interface for inter-language communication. In Windows Developer Preview, native C++ can communicate across the ABI with JavaScript and with the managed .NET languages C# and Visual Basic. This means you can create high-performance components in native C++ and consume them directly from one of these other languages. It also means you can consume Windows Runtime types directly in native C++, without having to interop with a managed layer as when you consume .NET Framework types.

At a low level, the new programming model is based on an updated version of COM, but the way that you program against this new model is more simple and natural than old-style COM programming. When you create a consumable Windows Runtime components or Metro style apps in native C++ you work primarily with classes and members just as in standard C++. JavaScript or .NET code instantiates your object by using new (or New) and the object is destroyed according to the mechanisms of the client language. When native C++ consumes a Windows Runtime object, destruction is handled by means of reference counting.

Download the code and extract the files.

"Cultivate optimism by committing yourself to a cause, a plan or a value system. You’ll feel that you are growing in a meaningful direction which will help you rise above day-to-day setbacks." — Dr. Robert Conroy

Note: The code is developed using Windows 8 & Visual Studio 2011 developer preview, which might change when the actual versions are released.

Under the hood Part 1 : C++ WinRT Component DLL & C#.NET application

In order to better understand  the concepts of WinRT, C#.NET, C++, etc. in the new Windows 8 environment, let us write some code. Then we will explore what happens under the hood when we compile code and run the applications. This will be explained in many parts as we progress.

First let us understand what WinRT is and what makes a WinRT DLL or WinRT component. There is no better place to start other than creating a WinRT component ourselves and examining it. So lets get started.

Creating a WinRT Component DLL:

Step 1:

Open VS 2011 Developer preview. Click on New Project. In the New Project Dialog, from Installed section, select Visual C++ in the left hand side navigation tree. Select WinRT Component DLL from the project templates and name the component as CppWinRTComponentDll. Click OK as shown in Fig 1.

Fig 1: Selecting Visual C++ template for WinRT Component DLL project.

Note: As a test, I tried to create a component with name C++WinRTComponentDll and VS 2011 C++ compiler shows many errors in the class files created by the wizard. So try to avoid ++ in the names.

Glimpse of new Visual Studio 2011 Developer preview edition:

In the new Solution Explorer, hover over the files and for each file you will find that there is an icon on the far right edge; View additional information (Ctrl+Right) icon.
When you select an item in Solution Explorer, whether it be a file or class or method, etc., the icon appears on the right edge of the selection. The tooltip says "View additional information (Ctrl+Right)". Clicking on the icon will invoke the "View Additional Information" menu which, for class files and members will provide relationships that you can view in Solution Explorer. Examples include "Base/Derived Types", "Find References", "Call Hierarchy", Calls, Is Called By, Is Used By etc. as shown in the following Fig 2.

Fig 2: Figure showing the View additional information (Ctrl+Right)icon.

Step 2:

Goto WinRTComponent.cpp file and delete the WinRTComponent definitions. Goto WinRTComponent.h and delete some of the default code. The code of the .h & .cpp files will look as shown in the following code snippets.

Code Snippet

// WinRTComponent.cpp

#include "pch.h"
#include "WinRTComponent.h"

using namespace CppWinRTComponentDll;

 

Code Snippet

#pragma once

using namespace Windows::Foundation;

namespace CppWinRTComponentDll
{

}
// WinRTComponent.h

 

We need the namespace CppWinRTComponentDll. Everything in WinRT has to be part of a namespace because the resolution of the DLL is based on a namespace that the class is in and that’s how other programming languages will find the class based on namespaces and DLL name.

Let us declare a sealed class called CalculatorSample in  WinRTComponent.h as shown in the following code snippet. The class is sealed as we don’t want others to derive from it. Sealed means no Inheritance.

Code Snippet

public ref class CalculatorSample sealed
{
public:
    int Add(int x, int y);
    int Sub(int x, int y);
    int Mul(int x, int y);

};

 

Why use Ref in front of the class:

Previously some of us worked on COM and created COM components. For that we have to create an interface, we have to specify that we are deriving from IUnknown (or derived) , put this in an MIDL file, use the MIDL Compiler to generate files, then go to C++ component, implement this interface, then create a class factory for it to create an instance and register this component. and the list goes on.. Well, all of this is done by using the keyword Ref in front of the class. So here we are creating WinRT Component that is accessible by dynamic languages as well. Here we are saying that CalculatorSample is a ref class, a class for WinRT. In other words, a ref class is a user-defined class that can be passed across the ABI boundary.

Step 3:

In the WinRTComponent.cpp, define the CalculatorSample  class member functions as shown in the following code snippet.

Code Snippet

int CalculatorSample::Add(int x, int y)
{
    return x+y;
}

int CalculatorSample::Sub(int x, int y)
{
    return x-y;
}

int CalculatorSample::Mul(int x, int y)
{
    return x*y;
}

 

So by now we have declared and defined the methods for the WinRT class called CalculatorSample. This class can be used by C++,C#.NET, VB.NET, JavaScript apps.

To sum it up, the WinRTComponent.h file should have the following code.

Code Snippet

#pragma once

using namespace Windows::Foundation;

namespace CppWinRTComponentDll
{

    public ref class CalculatorSample sealed
    {
    public:
        int Add(int x, int y);
        int Sub(int x, int y);
        int Mul(int x, int y);

    };
}
// WinRTComponent.h

WinRTComponent.cpp file contains the following code.

Code Snippet

// WinRTComponent.cpp

#include "pch.h"
#include "WinRTComponent.h"

using namespace CppWinRTComponentDll;

int CalculatorSample::Add(int x, int y)
{
    return x+y;
}

int CalculatorSample::Sub(int x, int y)
{
    return x-y;
}

int CalculatorSample::Mul(int x, int y)
{
    return x*y;
}

Step 4:

Do not Compile the project. pch.h and pch.cpp are like stdafx.h and stdafx.cpp in VC++ MFC.

This completes the creation of a WinRT Component DLL.

Let us create a new application and try to access the WinRT Component DLL that we just created. For that, I will use C#.NET, so that we can know how to call a WinRT Component DLL from C#.NET application.

Right Click on the Solution CppWinRTComponentDll, Click on Add and select the New Project menu item as shown in Fig 3.

Fig 3: Adding  a New project to the CppWinRTComponentDll solution.

Select Visual C# –> Application template and name the project as CSharpApplication as shown in Fig 4.

 

Fig 4: Creating a Visual C# Application project in VS 2011 Developer Preview.

Step 5:

Add a reference to the WinRT C++ calculator class we created to the C#.NET application as shown in the following figures.

Fig 5: Right click on References folder and Select Add Reference…

Fig 6: Select Solution tab in the left hand side navigation panel and select Projects. You should be able to see the CppWinRTComponentDll that we just created. Select CppWinRTComponentDll and click on Add button. click Close and go to step 6 if you have not encountered any error.

If you have compiled the C++ DLL by mistake before adding the reference, you will get a Failed to add reference dialog as shown below.

Fig 7: Failed to add reference dialog.

To fix the Failed to add reference dialog issue, clean up the CppWinRTComponentDll project as shown in the following figure 8.

Fig 8: Right Click on CppWinRTComponentDll  project, select Project Only, then select Clean Only CppWinRTComponentDll

Now repeat step 5 again to add a reference to the CppWinRTComponentDll and you should see the green circle icon with tick inside it as shown in Fig 9. This means the component is successfully referenced in the project.

Fig 9: Component successfully referenced in the project.

Click close.

Step 6:

Open MainPage.xaml file and add three text boxes to show the result of addition, subtraction and multiplication values returned from the C++ WinRT Component DLL.

Add the following XAML code.

Code Snippet

       <TextBox x:Name="txtAdd" HorizontalAlignment="Left" Text="TextBox" VerticalAlignment="Top" Margin="582,97,0,0" Height="36" Width="246" FontSize="20"/>
        <TextBox HorizontalAlignment="Left" Text="Calling Add method of C++ WinRT Component DLL" VerticalAlignment="Top" Margin="114,97,0,0"/>
       
        <TextBox x:Name="txtSub" HorizontalAlignment="Left" Text="TextBox" VerticalAlignment="Top" Margin="582,180,0,0" Height="36" Width="246" FontSize="20"/>
        <TextBox HorizontalAlignment="Left" Text="Calling Sub method of C++ WinRT Component DLL" VerticalAlignment="Top" Margin="114,180,0,0"/>
        
        <TextBox x:Name="txtMul" HorizontalAlignment="Left" Text="TextBox" VerticalAlignment="Top" Margin="582,260,0,0" Height="36" Width="246" FontSize="20">
        </TextBox>
        <TextBox HorizontalAlignment="Left" Text="Calling Mul method of C++ WinRT Component DLL" VerticalAlignment="Top" Margin="114,260,0,0"/>

 

Step 7:

Open MainPage.xaml.cs file and add the following code.

To use the C++ WinRT Component DLL that we just created we need to specify it in the C#.NET project by mentioning using CppWinRTComponentDll;

In the MainPage(), add the following code.

Code Snippet

CalculatorSample calcobj = new CalculatorSample();
            txtAdd.Text = calcobj.Add(10,20).ToString();
            txtMul.Text = calcobj.Mul(10, 20).ToString();
            txtSub.Text = calcobj.Sub(20, 10).ToString();

 

The complete MainPage.xaml file XAML code is

Code Snippet

<UserControl x:Class="CSharpApplication.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation&quot;
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml&quot;
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008&quot;
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006&quot;
    mc:Ignorable="d"
    d:DesignHeight="768" d:DesignWidth="1366">
    
    <Grid x:Name="LayoutRoot" Background="#FF0C0C0C">
        <TextBox x:Name="txtAdd" HorizontalAlignment="Left" Text="TextBox" VerticalAlignment="Top" Margin="582,97,0,0" Height="36" Width="246" FontSize="20"/>
        <TextBox HorizontalAlignment="Left" Text="Calling Add method of C++ WinRT Component DLL" VerticalAlignment="Top" Margin="114,97,0,0"/>
       
        <TextBox x:Name="txtSub" HorizontalAlignment="Left" Text="TextBox" VerticalAlignment="Top" Margin="582,180,0,0" Height="36" Width="246" FontSize="20"/>
        <TextBox HorizontalAlignment="Left" Text="Calling Sub method of C++ WinRT Component DLL" VerticalAlignment="Top" Margin="114,180,0,0"/>
        
        <TextBox x:Name="txtMul" HorizontalAlignment="Left" Text="TextBox" VerticalAlignment="Top" Margin="582,260,0,0" Height="36" Width="246" FontSize="20">
        </TextBox>
        <TextBox HorizontalAlignment="Left" Text="Calling Mul method of C++ WinRT Component DLL" VerticalAlignment="Top" Margin="114,260,0,0"/>

    </Grid>
    
</UserControl>

 

The complete MainPage.xaml.cs file C#.NET code is

Code Snippet

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Data;
using CppWinRTComponentDll;

namespace CSharpApplication
{
    partial class MainPage
    {
        public MainPage()
        {
            InitializeComponent();

            CalculatorSample calcobj = new CalculatorSample();
            txtAdd.Text = calcobj.Add(10,20).ToString();
            txtMul.Text = calcobj.Mul(10, 20).ToString();
            txtSub.Text = calcobj.Sub(20, 10).ToString();
            

        }
    }
}

 

Step 8: Build the solution.

The following information will be displayed in the output window. See the highlighted information. The Visual Studio 2011 is compiling the projects as well as deploying the projects. Later, we will see in detail what happens during deployment and how the applications is run by Windows 8.

1>—— Build started: Project: CSharpApplication, Configuration: Debug Any CPU ——
1>  CSharpApplication -> C:\Users\Prathima\Documents\Visual Studio 11\Projects\CppWinRTComponentDll With CSharp App\CSharpApplication\bin\Debug\csharpapplication.exe
1>  CSharpApplication -> C:\Users\Prathima\Documents\Visual Studio 11\Projects\CppWinRTComponentDll With CSharp App\CSharpApplication\bin\Debug\CSharpApplication.build.appxrecipe
2>—— Deploy started: Project: CSharpApplication, Configuration: Debug Any CPU ——
========== Build: 1 succeeded, 0 failed, 1 up-to-date, 0 skipped ==========
========== Deploy: 1 succeeded, 0 failed, 0 skipped ==========

 

The output of the programs is the application

Download the source code from here.

"The future belongs to those who see possibilities before they become obvious."  - John Scully

Note: This code is developed using Windows 8 & Visual Studio 2011 developer preview, which might change when the actual versions are released.

Part 3: Introduction to WinRT, the new ‘Windows Runtime’ in Windows 8

To install visual studio 2011 developer preview + Window 8 beta, refer to post here.

To get started working with Windows 8 operating system, see post here.

Fig 1: Windows 8 Platform and Tools slide shared at Build conference.

Windows Runtime, or shortly WinRT, is Microsoft’s new programming model that makes the backbone of the new Metro-style apps (also known as Immersive) in the new Windows 8 operating system. WinRT solves many of the problems of Win32, from an apps perspective. Apps created for WinRT are safe, secure, and sandboxed, can’t wreck other apps and all install in just 2-3 seconds. They feature isolated storage, single folder installs (as per the Mac), and require user consent to access the general file system. This is part of it, a modern, truly different app platform that is far more different, and far more capable, than many people understand right now.

WinRT isn’t another abstraction layer; it’s a new runtime sitting directly on top of the Windows Kernel Services just like the good old Win32 API as shown in the above figure that allows developers to write Metro style applications for Windows 8, using a variety of languages including C++ (with WRL or  with Component Extensions – C++/CX), the managed languages C# and VB.NET, as well as JavaScript. In the above figure, right on top of NT kernel (like Win32) is WinRT. This WinRT has an application model and three boxes of capabilities that are expressed by APIs (Communications & Data, Graphics & Media, and Devices & Printing). "Above" WinRT is the two sets of presentation layer/programming language couples: XAML and various high level programming languages (C#, VB, and so on) and HTML/CSS and JavaScript, respectively. (DirectX is left out, but sits on top of WinRT too.) WinRT is an unmanaged native layer and its API is object oriented that can be consumed both from native or managed languages, as well as JavaScript. In short, WinRT is the Object Oriented Programming replacement for Win32.

This marks the first major break in the core of Windows since Win32 was introduced in 1993 with Windows NT. WinRT represents a new application execution environment with semantics that are very different than Win32. Unlike Win32, which was designed with C in mind, the WinRT APIs are written in C++ and designed from the beginning to be object oriented. Consistency, ease of use, and performance are key aspects of the new runtime API. Every object in the WinRT API supports reflection so that even dynamic languages such as JavaScript can use them efficiently. Along with this comes a unified object model, a rarity for C++ based libraries. The new Windows SDK for Metro style apps also includes a subset of traditional Win32, Component Object Model (COM), and .NET Framework APIs, as well as HTML5 and CSS3 APIs that are accessible to Metro style app developers. I.e. Metro style apps can use a subset of the Win32 and COM API. This subset of APIs was chosen to support key scenarios for Metro style apps that were not already covered by the Windows Runtime, HTML/CSS, or other supported languages or standards. The Windows App Certification Kit ensures that your app uses only this subset of the Win32 and COM API. The subset of the Win32 and COM API that can be used in a Metro style app is indicated in the header files in the Windows Software Development Kit (SDK) for Metro style Apps. Look for the following statements in the header files:

#pragma region Application Family

#pragma region Desktop Family

The compiler and object browser in Microsoft Visual Studio 11 Express for Windows Developer Preview use these statements to determine whether to show or hide a Win32 or COM API element.

One other big change is that all WinRT components have metadata available for them, just like .NET assemblies. Well, the Windows Runtime is exposed using API metadata stored in .winmd files as shown in the following figure 2. In COM you were able to achieve that with type libraries(Type libraries contain metadata that represent COM types), but not every COM component had them.  The metadata (API definitions) of WinRT contained in .winmd files are encoded in ECMA 335 metadata format, the same format that .NET uses but with a few modifications. The underlying binary contract makes it easy for you to access the Windows Runtime APIs directly in the development language of your choice. The shape and structure of the Windows Runtime APIs can be understood by both static languages such as C# and dynamic languages such as JavaScript. IntelliSense is available in JavaScript, C#, Visual Basic, and C++. This common metadata format allows for significantly less overhead when invoking WinRT from .NET applications compared to a P/Invoke, and much simpler syntax. Regular C++ (with COM-specific discipline) can also be used to program with WinRT components, with the help of new template library called Windows Runtime C++ Template Library (WRL), which is similar in purpose to what Active Template Library provides for COM. The MSDN documentation, however, recommends using C++/CX instead of WRL.

Fig showing the “C:\Program Files (x86)\Windows Kits\8.0\Windows Metadata\” folder in Windows 8 Developer Preview. You can observe that they are actually CLI assemblies with no code, just metadata tables.

Fig 2: Windows RunTime Metadata files

As shown in the following Fig 3, you can open the .winmd file with ILDASM. Note, this doesn’t mean that WinRT itself is managed – it simply reuses the file format.

Fig 3: Opening an C:\Program Files (x86)\Windows Kits\8.0\Windows Metadata\Windows.Applicationmodel.Activation.winmd file using ILDASM

For the structure of the Windows Runtime, see the Microsoft site.

There are a number of libraries implemented in terms of the new object model, i.e. defining WinRT interfaces and classes. Look at “Windows Metadata” folder mentioned above to see what’s there; or just fire up Object Browser in VS and select “Windows 8.0″ in the framework selector, to see what’s covered. There’s a lot there, and it doesn’t deal with UI alone – you also get namespaces such as Windows.Data.Json, or Windows.Graphics.Printing, or Windows.Networking.Sockets. Then you get several libraries, which are specifically dealing with UI – mostly these would be various namespaces under Windows.UI or Windows.UI.Xaml. A lot of them are very similar to WPF/Silverlight namespaces – e.g. Windows.UI.Xaml.Controls is closely matching System.Windows.Controls; also for Windows.UI.Xaml.Documents etc.

The WinRT type system relies strongly on WinRT components, which are COM objects implementing a specific set of interfaces and adhering to a certain ABI (Application Binary Interface). WinRT is essentially a COM-based API, relying on an enhanced COM that implements the IInspectable interface. The IInspectable interface enables projecting Win32 and COM features into JavaScript and other languages, such as C# and Visual Basic. Implement the IInspectable interface when you want your class to be available in other programming environments. The IInspectable interface is the base interface for all Windows Runtime classes. All Windows Runtime classes must implement the IInspectable interface. The IInspectable interface inherits from the IUnknown interface. so every WinRT object implements IUnknown and does refcounting (WinRT objects are reference counted like COM for memory management, with weak references to avoid circularity), and builds from there. It does add quite a lot of new concepts in comparison to COM of old, most of which come directly from .NET – for example, WinRT object model has delegates, and events are done .NET-style (with delegates and add/remove subscriber methods, one per event) rather than the old COM model of event sources and sinks. Of other notable things, WinRT also has parameterized (“generic”) interfaces. 

In short, Windows Runtime is a new set of libraries exposing Windows functionality and available to JavaScript/C#/VB/C++ as shown in figure 4. Each language has been made to understand and be able to call them directly rather than having to go through some thunking layer. Silverlight and WPF are flavors of XAML that run on the CLR. Among other functionality, Windows Runtime exposes a version of XAML very similar to Silverlight, but does so in a native way, not via the CLR. It can be accessed from the CLR, but also from C++.

Fig 4 : Microsoft Windows 8 Platform and Development Tools

Relation between .NET & WinRT

The important concept to understand is that the .NET framework now has two profiles.

1. .NET Metro profile (CLR that deal with Metro application)
2. .NET Client profile (CLR runtime for C#,VB.NET applications)

The .NET APIs for Metro style apps provide a set of managed types that you can use to create Metro style apps for Windows using C# or Visual Basic. The .NET APIs for Metro style apps include a subset of types from the .NET Framework and enable .NET developers to create Metro style apps within a familiar programming framework. You use these types with types from the Windows Runtime API to create Metro style apps.

In some cases, a type that you used in a .NET Framework application does not exist within the .NET APIs for Metro style apps; instead, you must use a type from the Windows Runtime. For example, the System.IO.IsolatedStorage.IsolatedStorageSettings class is not included in the .NET APIs for Metro style apps; instead, you use the Windows.Storage.ApplicationDataContainer class for app settings. You retrieve an instance of the ApplicationDataContainer class through the Windows.Storage.ApplicationData.Current.LocalSettings property.

• The .NET Framework 4.5 is used in both Desktop Mode apps and in Metro style apps. There is a difference though. Metro style apps use what is best described as a different .NET Profile (e.g. Desktop apps use the .NET Client Profile and Metro style apps use the .NET Metro Profile). There is NOT actually a different profile, but the implementation of .NET in Metro style apps is LIKE a different profile. Don’t go looking for this profile – its basically rules built into the .NET Framework and CLR that define what parts of the framework are available.
• There is only one CLR. Each application or application pool (depending on the app type) spins up a process and the CLR is used within that process. Meaning, a Metro style app and a Desktop Mode app running at the same time are using the same CLR bits, but separate instances of the CLR.
• Whether a Desktop Mode app or a Metro style app, if it is a .NET app, it is compiled to the same MSIL. There isn’t a special Windows 8 Metro IL – there is, like the CLR, only one MSIL.

In the above diagram (Fig 4) you can see that the CLR and the .NET Framework 4.5 are used for C# and Visual Basic apps in either Desktop Mode apps (blue side) or Metro style apps (green side). Silverlight is still only available in Desktop Mode as a plug-in to Internet Explorer (yes, out of browser is still supported in Desktop Mode). Another addition in this diagram is DirectX, which was strangely absent from the original diagram. DirectX is the defacto technology for high-polygon count applications, such as immersive games. DirectX leverages the power of C++.

This biggest confusion, has been around the use of the .NET Framework across the blue side and green side. The reason for the .NET Metro Profile is because the Metro style apps run in an app container that limits what the application can have access to in order to protect the end user from potentially malicious apps. As such, the Metro Profile is a subset of the .NET Client Profile and simply takes away some of the capabilities that aren’t allowed by the app container for Metro style apps. Developers used to .NET will find accessing the WinRT APIs very intuitive – it works similarly to having an assembly reference and accessing the members of said referenced assembly.

Additionally, some of the changes in the Metro Profile are to ensure Metro style apps are constructed in the preferred way for touch-first design and portable form factors. An example is File.Create(). Historically if you were using .NET to create a new file you would use File.Create(string fileLocation) to create the new file on the disk, then access a stream reader to create the contents of the file as a string. This is a synchronous operation – you make the call and the process stalls while you wait for the return. The idea of modern, Metro style apps is that asynchronous programming practices should be used to cut down on things like IO latency, such as that created by file system operations. What this means is that the .NET Metro Profile doesn’t provide access to File.Create() as a synchronous operation.

Ultimately all of this means that you have some choice, but you don’t have to sacrifice much if anything along the way. You can still build .NET and Silverlight apps the way you are used to, and they will run on Windows for years to come. If you want to build a new Metro style app, you have four options to choose from:

1. XAML and .NET (C# or VB): You don’t have to giving up too much in the .NET Framework (remember, you only give up what is forbidden by the Application Container), and you get access to WinRT APIs for sensor input and other system resources.
2. XAML and C++: You can use your skills in XAML and C++ in order to leverage (or even extend) WinRT. Of course you don’t get the benefit of the .NET Framework. You can use WRL or  with Component Extensions – C++/CX
3. HTML and JavaScript: You can leverage the skills you have in UI layout, and make calls from JavaScript to WinRT for access to system resources, and sensor input.
4. DirectX and C++: If you’re building an immersive game you can use DirectX and access the device sensors and system resources through C++ and WinRT.

Fig 5 : Deciphering the new WinRT – Metro style application API’s.

.NET with WinRT:

C#/VB: The end of P/Invoke : Calling native functions from .NET usually involves building up structures and manipulating pointers. Under WinRT all APIs are exposed as objects that C# and VB can consume directly. This puts .NET developers on level footing with C++ developers.

Application responsiveness is very important to Microsoft. In order to convey that to developers all OS-level API calls that take longer than 50 milliseconds will be exposed as an asynchronous operation.

Fig showing the overview of CLR components.

A managed Metro application (e.g. written in C#) will still load the CLR.  The CLR version bundled with the preview is 4.0.30319.17020, and that’s the version that gets loaded inside a Metro app.  Symmetrically, a “fully” .NET application (e.g. a WinForms app) can reference the WinRT metadata assemblies and use WinRT APIs. This will be a necessity in some cases, for example to tap into the WinRT sensor APIs.

.NET has the ability to directly reference WinRT components as if they were .NET assemblies. This works differently from COM Interop – you don’t need any intermediate artifacts such as interop assemblies, you just read a .winmd file, and all types and their members in its metadata become visible to you as if they were .NET objects. Note that native C++ programs that use WinRT do not require CLR at all (WinRT libraries themselves are fully native) – the magic to expose all that stuff as managed is inside the CLR itself, and is fairly low level. If you ildasm a .NET program that references a .winmd, you’ll see that it actually looks like an extern assembly reference – there’s no sleight of hand trickery such as type embedding there.

It’s not a blunt mapping, either – CLR tries to adapt WinRT types to their equivalents, where possible. So e.g. GUIDs, dates and URIs become System.Guid, System.DateTime and System.Uri, respectively; WinRT collection interfaces such as IIterable and IVector become IEnumerable and IList; and so on. This goes both ways – if you have a .NET object that implements IEnumerable, and pass it back to WinRT, it’ll see it as IIterable.

Some developers are confused as to whether .NET is there or not in the first place, as not all of the .NET APIs are present (File I/O, Sockets), many were moved and others were introduced to integrate with WinRT. When you use C# and VB, you are using the full .NET framework. But they have chosen to expose a smaller subset of the API to developers to push the new vision for Windows 8. And this new vision includes safety/sandboxed systems and asynchronous programming. This is why you do not get direct file system access or socket access and why synchronous APIs that you were used to consuming are not exposed. What they did was that they only exposed to the compiler a set of APIs when you target the Metro profile. So your application will not accidentally call File.Create for example. At runtime though, the CLR will load the full class library, the very one that contains File.Create, so internally, the CLR could call something like File.Create, it is just you that will have no access to it. So for managed applications, the Metro projects in Visual Studio are targeting a special subset of the .NET framework, and will not have access to all the classes – not even all the classes of the .NET Client Profile. For example, the System.IO.FileStream class is not available.

Although these limitations may seem artificial, annoying, and counterproductive, there is probably a good reason for having them. The Metro UI and Metro apps are a fresh start for Windows applications and their developers. There is no trivial way to port an existing UI app to Metro without a considerable UI redesign. It’s also a great opportunity to enforce additional limitations that make sure Metro apps respect the user’s privacy, conserve battery power, integrate well with the UI guidelines, and live in harmony within the application sandbox.

Ultimately, what this means is that your .NET Metro apps get access to a subset of the existing standard .NET libraries, and also to (native) WinRT libraries, some of which – particularly Windows.UI – look very similar to Silverlight, API-wise. You still have XAML to define your UI, and you still deal with the same basic concepts as in Silverlight – data bindings, resources, styles, templates etc. In many cases, it is possible to port a Silverlight app simply by using the new namespaces, and tweaking a few places in code where the API was adjusted. WinRT itself doesn’t have anything to do with HTML and CSS, and it bears relation to JavaScript only in a sense that it is also exposed there, similar to how it is done for .NET. You don’t need to deal with HTML/CSS/JS when you use WinRT UI libraries in your .NET Metro app.

C++11 with WinRT: C++ Development

A good news for C++ developers is that User interfaces in C++ will be written primarily in XAML for immersive applications. However, this is not available for classical, Win32 applications. This libraries for working with XAML have all been ported to C++ and are compiled to native x86. Metro applications written with XAML and C++ do not run on top of .NET, they get compiled directly to x86 just like any other Visual C++ application. Calling methods on UI controls is just like calling methods on any other object in C++.

Microsoft has created a new language called C++ Component Extension, or simply C++/CX. While the syntax is very similar to C++/CLI, the language is not managed, it’s still native. WinRT components built in C++/CX do not compile to managed code, but to 100% native code.

App Container and Application Permissions : Metro applications run in what’s known as the “app container”. This appears to replace the windowing environment used by Win32 based applications.

Most API calls are sent directly to the underlying kernel. Some, however, some will be routed through the system broker. The system broker ensures that applications can only access features that the user has approved. For example, the first time an application tries to access the camera the service broker will prompt the user for their approval. Applications are required to include a manifest that indicates all of the restricted services the application may need. This model will be very familiar to mobile device developers.

All Metro applications run within WinRT’s app container and thus are monitored by the system broker, even those written in C++. The idea is to limit the ability of applications to damage the system. While probably not impossible, building malware with WinRT will be much harder than it is in Win32.

Overlapping Windows No Longer Exist : In Metro, there are no overlapping top-level windows. There’s still Popup (http://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.xaml.controls.primitives.popup). Dialog boxes, a core concept from previous versions of Windows, does not exist in WinRT. The performance cost and usability concerns are simply no longer justifiable to Microsoft. Applications that wish to use this pattern will have to develop other ways to express things such as message boxes. Another library that didn’t make it into WinRT is GDI. If an application is going to use the Metro interface it needs to do so from top to bottom, it appears that mixing Metro and classic user interfaces is not possible.

PlayTo Contract : Another contract that is being exposed is PlayTo. This allows applications to send media files such as audio and video to a charm. The charm will then allow the user to choose which application they want to use to view the file. Presumably these aren’t just physical files, but rather any form of media that can be expressed as a data stream.

All Metro Applications Must be Digitally Signed: Anonymous applications are not allowed. Applications can be self-signed for testing, but by the time they appear in the app store they will need to be signed using a real certificate.

JavaScript :

Another major language for Windows 8 is JavaScript. While it doesn’t use XAML, it does have direct access to the underlying WinRT API just like native and .NET applications. This isn’t just a container like PhoneGap, JavaScript developers get the same rich API that other developers use. Since this is JavaScript the UI toolkit of choice is HTML and CSS rather than XAML. The same rendering engine used by Internet Explorer 10 us used by Metro JavaScript applications, though they don’t actually run in a browser. A JavaScript application looks just like any other Metro application. Expression Blend 5 now supports editing HTML5, much like you use it for editing XAML.

User controls in JavaScript are nearly on par with those in C++ and .NET. Some controls are intrinsic to the HTML rendering engine, others are written in JavaScript. These JavaScript based ones are div based much like controls built using jQuery.

The IInspectable interface contains three methods: GetIids, which returns the interfaces implemented by the component; GetRuntimeClassName, which returns the fully-qualified name of the component; and GetTrustLevel, which returns the component’s trust level that can be used to control component activation.

IInspectable is used by the dynamic language bindings from JavaScript. Given a reference to a WinRT component, the JavaScript interpreter can call the IInspectable::GetRuntimeClassName method and obtain the fully-qualified class name of the WinRT component. Using the namespace name the interpreter can ask Windows to load the metadata file (.winmd) describing the component, and from the metadata determine how to use the interfaces implemented by the component.

WinRT Projections

What we call "bindings" Microsoft now calls "projections". Projections are the process of exposing APIs to three environments: Native (C and C++), HTML/JavaScript and .NET.  If you author a component in C++ or a .NET language, its API will be stored in a WinMD file and you will be able to consume it from all three environments (Native, JavaScript and .NET). Even in C++ you are not exposed to COM. The use of COM is hidden behind the C++ projection tools. You use what looks and feels like a C++ object oriented API. To support the various constructs of WinRT, the underlying platform defines a basic set of types and their mappings to various environment. In particular, collection objects in WinRT are mapped to constructs that are native to each environment.

Conclusion:

WinRT solves many of the problems of Win32, from an apps perspective. Apps created for WinRT are safe, secure, and sandboxed, can’t wreck other apps, can’t cause "Windows rot," and all install in just 2-3 seconds. They feature isolated storage, single folder installs (as per the Mac), and require user consent to access the general file system.

To summarize, WinRT does not replace .NET, nor does it compete with .NET – and the same applies to Win32. You can write server and client applications using .NET, including WPF and Silverlight. You can write server and client applications using C++, including Win32 and MFC. However, if you choose to believe in the Metro way, you can write Metro applications for Windows 8 using .NET languages or using C++ or using JavaScript, with a consistent set of APIs exposed through WinRT. At the same time the Win32 applications will continue to run just as before and you can still (and most certainly will) develop Win32 applications.

Finally, I am very impressed with the details of Windows 8! It’s fantastic. There are three ways to write WinRT applications. One is C++, in which case you write directly to the “projection” of WinRT into your language. The second is .NET, in which case your code goes via the CLR. The third is HTML and JavaScript, in which case your code goes via the “Chakra” JavaScript engine also used by Internet Explorer 9 and higher. There is no message loop in WinRT. There is no GDI in WinRT. All graphics are via DirectX. XNA, the .NET games framework, is not supported. The WinMD (Windows Metadata – which makes the whole Windows Metro API available to any language – hence the ability to use JavaScript, for example) is great. The new object-oriented API, with namespaces and interfaces etc., is great. The language projections are great. Oh and the native support in Microsoft C++!! for the Windows Runtime, and the fact that C++ is ideal for it (since it is, at the core, an extension of COM), is great. So much to learn!!

A great leader’s courage to fulfill his vision comes from passion, not position. - Paul John Maxwell

Introduction to Command Binding

We have seen the abc’s of Data Binding here. If you have worked in VC++, then you are aware of some of the semantics of WPF command binding. Basically, commands are nothing but actions performed on the applications using input mechanism. commands are abstract and loosely-coupled version of events. Whereas events are tied to details about specific user actions (such as a Button being clicked or a List Item being selected), commands represent actions independent from their user interface exposure. Canonical examples of commands are Cut, Copy, and Paste. In VC++ MFC, we declare commands and then define the functions that execute the command action. Similarly, in WPF, the semantics and the object that invokes a command is separated from the logic that executes the command. This allows for multiple and disparate sources like MenuItems in a Menu, MenuItems on a Context Menu(Right Click), Buttons on a ToolBar, keyboard shortcuts(CTRL+X for Cut), and so on, to invoke the same command logic, and it allows the command logic to be customized for different targets. We used to perform similar design in VC++ too.

In VC++ MFC application, for example, the editing operations Copy, Cut, and Paste, can be invoked by using different user actions if they are implemented by using commands. An MFC application might allow a user to cut selected text by either choosing an Cut item in edit menu, or Cut in right click menu, or using a key combination, such as CTRL+X. By using commands, you can bind each type of user action to the same logic. In VC++, we assign ID’s to each command like ID_EDIT_COPY, ID_EDIT_CUT and ID_EDIT_PASTE. WPF supports similar concepts but uses a different mechanism to achieve it. By using commands, you can bind each type of user action to the same logic. Another purpose of commands is to indicate whether an action is available. To continue the example of cutting an object or text, the action only makes sense when something is selected. If a user tries to cut an object or text without having anything selected, nothing would happen. To indicate this to the user, many applications disable buttons and menu items so that the user knows whether it is possible to perform an action.

A command is any object implementing the ICommand interface (from System.Windows.Input), which defines two methods and one event:

• Execute—The method that executes the command-specific logic
• CanExecute—A method returning true if the command is enabled or false if it is disabled
• CanExecuteChanged—An event that is raised whenever the value of CanExecute changes

Steps to create a Command:

1. Say you want to create a Cut Command. We need to implement a class that implements ICommand.
2. Call Execute from relevant event handlers (when CanExecute returns true)
3. Handle the CanExecuteChanged event to toggle the IsEnabled property on the relevant pieces of user interface.

Fortunately, controls such as Button, CheckBox, and MenuItem have logic to interact with any command on your behalf. They expose a simple Command property (of type ICommand). When set, these controls automatically call the command’s Execute method (when CanExecute returns true) whenever their Click event is raised. In addition, they automatically keep their value for IsEnabled synchronized with the value of CanExecute by leveraging the CanExecuteChanged event. By supporting all this via a simple property assignment, all of this logic is available from XAML. Some of WPF’s controls have built-in behavior tied to various commands. 

WPF’s built-in commands like Cut, Copy, Paste are exposed as static properties and they are all instances of RoutedUICommand, a class that not only implements ICommand, but supports bubbling just like a routed event. A command can indicate whether an action is possible by implementing the CanExecute method. A button can subscribe to the CanExecuteChanged event and be disabled if CanExecute returns false or be enabled if CanExecute returns true.

WPF defines a bunch of commands already, so you don’t have to implement ICommand objects for Cut, Copy, and Paste and worry about where to store them. WPF’s built-in commands are exposed as static properties of five different classes:

• ApplicationCommands—Close, Copy, Cut, Delete, Find, Help, New, Open, Paste, Print, PrintPreview, Properties, Redo, Replace, Save, SaveAs, SelectAll, Stop, Undo, and more
• ComponentCommands—MoveDown, MoveLeft, MoveRight, MoveUp, ScrollByLine, ScrollPageDown, ScrollPageLeft, ScrollPageRight, ScrollPageUp, SelectToEnd, SelectToHome, SelectToPageDown, SelectToPageUp, and more
• MediaCommands—ChannelDown, ChannelUp, DecreaseVolume, FastForward, IncreaseVolume, MuteVolume, NextTrack, Pause, Play, PreviousTrack, Record, Rewind, Select, Stop, and more
• NavigationCommands—BrowseBack, BrowseForward, BrowseHome, BrowseStop, Favorites, FirstPage, GoToPage, LastPage, NextPage, PreviousPage, Refresh, Search, Zoom, and more
• EditingCommands—AlignCenter, AlignJustify, AlignLeft, AlignRight, CorrectSpellingError, DecreaseFontSize, DecreaseIndentation, EnterLineBreak, EnterParagraphBreak, IgnoreSpellingError, IncreaseFontSize, IncreaseIndentation, MoveDownByLine, MoveDownByPage, MoveDownByParagraph, MoveLeftByCharacter, MoveLeftByWord, MoveRightByCharacter, MoveRightByWord, and more

Each of these properties does not return a unique type implementing ICommand. Instead, they are all instances of RoutedUICommand, a class that not only implements ICommand, but supports bubbling just like a routed event.

Lets develop a dialog that has a “Help” button, when clicked will open the help webpage. Let’s demonstrate how these built-in commands work by attaching some logic with the Help command defined in ApplicationCommands. Assuming the Button is named helpButton, you can associate it with the Help command in C# as follows:

helpButton.Command = ApplicationCommands.Help;

All RoutedUICommand objects define a Text property containing a name for the command that’s appropriate to show in a user interface. (This property is the only difference between RoutedUICommand and its base RoutedCommand class.) For example, the Help command’s Text property is (unsurprisingly) set to the string Help. The hard-coded Content on this Button could therefore be replaced as follows:

helpButton.Content = ApplicationCommands.Help.Text;

If you were to run the dialog with this change, you would see that the Button is now permanently disabled. That’s because the built-in commands can’t possibly know when they should be enabled or disabled, or even what action to take when they are executed. They delegate this logic to consumers of the commands. To plug in custom logic, you need to add a CommandBinding to the element that will execute the command or any parent element (thanks to the bubbling behavior of routed commands). All classes deriving from UIElement (and ContentElement) contain a CommandBindings collection that can hold one or more CommandBinding objects. Therefore, you can add a CommandBinding for Help to the dialog’s root Window as follows in

<Window.CommandBindings>
        <CommandBinding Command="Help"
                        CanExecute="CommandBinding_CanExecute"
                        Executed="CommandBinding_Executed" />
    </Window.CommandBindings>

 

Or in its code-behind file:

this.CommandBindings.Add(new CommandBinding(ApplicationCommands.Help,
        CommandBinding_Executed, CommandBinding_CanExecute));

The methods called CommandBinding_Executed and CommandBinding_CanExecute have to be defined in code behind file as follows. These methods will be called back at appropriate times in order to plug in an implementation for the Help command’s CanExecute and Execute methods.

private void CommandBinding_CanExecute(object sender, CanExecuteRoutedEventArgs e)
{
    if (firstName.Text == "help")
        e.CanExecute = true;
    else
        e.CanExecute = false;

}

private void CommandBinding_Executed(object sender, ExecutedRoutedEventArgs e)
{
    System.Diagnostics.Process.Start("http://kishore1021.wordpress.com/&quot;);

}

 

In the XAML file, assign the command to the help button as follows.

<Button Grid.Row="3" Grid.Column="1" Command="Help"
          Name="MyHelpButton" Margin="4,190,0,5">
            Help
        </Button>

 

Compile the project and run the application. Initially, the help button is disabled. Enter help in the first name textbox and you can see that the help button is enabled. Now to take advantage of command binding, say you want to bring up help when user presses keyboard shortcut F2 key. We can bind our own input gestures to a command by adding KeyBinding and/or MouseBinding objects to the relevant element’s InputBindings collection in code as follows

this.InputBindings.Add(
              new KeyBinding(ApplicationCommands.Help, new KeyGesture(Key.F2)));

The same binding can be performed in XAML as follows

<Window.InputBindings>
    <KeyBinding Command="Help" Key="F2"/>
    <KeyBinding Command="NotACommand" Key="F1"/>
</Window.InputBindings>

 

The complete XAML code is

<Window x:Class="CommandBinding101.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation&quot;
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml&quot;
        Title="MainWindow" Height="350" Width="525">
    <Window.CommandBindings>
        <CommandBinding Command="Help"
                        CanExecute="CommandBinding_CanExecute"
                        Executed="CommandBinding_Executed" />
    </Window.CommandBindings>
    <Window.InputBindings>
        <KeyBinding Command="Help" Key="F2"/>
        <KeyBinding Command="NotACommand" Key="F1"/>
    </Window.InputBindings>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="30"/>
            <RowDefinition Height="30"/>
            <RowDefinition Height="30"/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>

        <Label>
            Enter your first name:
        </Label>
        <TextBox Grid.Row="0" Grid.Column="1"
           Name="firstName" Margin="0,5,10,5"/>

        <Label Grid.Row="1" >
            Enter your last name:
        </Label>
        <TextBox Grid.Row="1" Grid.Column="1"
           Name="lastName" Margin="0,5,10,5"/>

        <Button Grid.Row="2" Grid.Column="0"
          Name="Clear" Margin="2" Click="Clear_Click">
            Clear Name
        </Button>

        <Button Content="Enable Help" Margin="2" Name="button1" Grid.Column="1" Grid.Row="2" Click="button1_Click" />
        
        <Button Grid.Row="3" Grid.Column="1" Command="Help"
          Name="MyHelpButton" Margin="4,190,0,5">
            Help
        </Button>
        <Label Content="Type help in the first name edit box to enable the Help button" Margin="-1,13,12,164" Grid.Row="3" Grid.ColumnSpan="2" />
    </Grid>
    
</Window>

The complete code behind is

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace CommandBinding101
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            //MyHelpButton.Command = ApplicationCommands.Help;

           // this.CommandBindings.Add(new CommandBinding(ApplicationCommands.Help,
           //  CommandBinding_Executed, CommandBinding_CanExecute));

            //this.InputBindings.Add(
            //  new KeyBinding(ApplicationCommands.Help, new KeyGesture(Key.F2)));

        }

        private void CommandBinding_CanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            if (firstName.Text == "help")
                e.CanExecute = true;
            else
                e.CanExecute = false;

        }

        private void CommandBinding_Executed(object sender, ExecutedRoutedEventArgs e)
        {
            System.Diagnostics.Process.Start("http://kishore1021.wordpress.com/&quot;);

        }

        private void Clear_Click(object sender, RoutedEventArgs e)
        {
            firstName.Clear();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            firstName.Text = "help";
        }
    }
}

If you use one of the preexisting RoutedUICommand objects for a WPF command, e.g. ApplicationCommands.Open, you’ll notice that the RoutedUICommand instance has a Text property.  This property in the command is used to set the label appearing on any MenuItem instances that have attached to the command by setting their Command property.  You don’t need to set the menu item’s Header property explicitly.

Download the source code here

If you really want the key to success, start by doing the opposite of what everyone else is doing.