Using .NET from C++

Question

After a lot of reading, I'm still confused about using .NET from a C++ Metro style app.

Many documents note that Metro apps can use a subset of .NET (as well as WinRT, of course). How does this work? Does C++/CX handle all the plumbing, or what?

Are there any samples?

Answer 1

A Metro style app written using C++ does not utilize the .Net framework. It is compiled to native code. No CLR involved. If you are wanting to access the .Net namespaces avalable to a Metro style app, you could build a VB or C# Class Library to consume from your C++ app. This talk demonstrates mixing the two in the same solution (but the reverse of your ask, using C# app with C++ WinMD). I would suggest this talk for any C++ developer getting started with Metro style app development.

Under the covers with C++ for Metro style apps
TOOL-690C
Speakers: Deon Brewis

Thanks,

-David

Answer 2

No public samples that I know of. If you create a C# Metro Class Library (this is different from the older C# Class Library) you'll see in the Project properties 'Output type' drop down a 'WinMD File' selection. You can use this to build C# to a winmd. Note that this winmd contains both windows metadata and IL (so no need for an assembly dll).

In the C++/CX project, add the winmd file generated above and then just ref new the class:

App::App()
{
    InitializeComponent();

	ClassLibrary1::Class1^ c = ref new ClassLibrary1::Class1();
	String^ s = c->GetAString();
}

Make sure in the Add References dialog that you use the browse button and point directly to the ClassLibrary1.winmd file -- a project reference to ClassLibrary1.csproj will not work.

You'll also need to add the 'sealed' keyword to the C# class when building as a winmd:

namespace ClassLibrary1
{
    public sealed class Class1
    {
        public string GetAString() { return "Hello World"; }
    }
}