# Registration-free WinRT in C# Desktop App sample

This sample demonstrates how to use [Registration-free WinRT](https://aka.ms/regfreewinrtblog) a new feature in Windows 10 Version 1903 to reference a C++ Windows Runtime component in a non-packaged C# desktop app. It contains a C# console app (CSharpConsole.csproj) and a WinRT Component (WinRTComponent.vcxproj).

You can learn more about Registration-free WinRT [here](https://aka.ms/regfreewinrtblog).

The C# desktop app uses:

* The [Microsoft.VCRTForwarders.140](https://aka.ms/vcrtfwdnuget) NuGet package to manage C++ Runtime dependencies for the C++ component. The GitHub repo can be found [here](https://aka.ms/vcrtfwdgit).

## Requirements

The sample requires Windows 10 Version 1903.

## Instructions

### C# app

A non-packaged C# console app referencing a C++ WinRT Component

* The C# app has a visual Studio reference to the WinRTComponent Project. To add a VS reference to a project right click on the project, then select Add, Reference, Projects, then select the target project to reference.

* The specific DLLs and classes (from the WinRT component) being referenced should be declared in the [Win32 Application manifest](https://docs.microsoft.com/en-us/windows/desktop/SbsCs/application-manifests) - CSharpConsoleApp.exe.manifest.

To add a new Win32 Application Manifest to a desktop app, right click on the project, then select Add, New Item, General, Application Manifest File, and name it yourappname.exe.manifest.

* For the system to locate the component DLLs specified in the application manifest at runtime, the DLLs must be in the same directory as the app's .exe. This project uses a Post Build Event to copy the component DLL to the app's output directory:

````
copy /Y "$(SolutionDir)WinRTComponent\bin\$(Platform)\$(Configuration)\WinRTComponent.dll"  "$(SolutionDir)$(MSBuildProjectName)\$(OutDir)WinRTComponent.dll" 

````
* To add your own Post Build Event to your C# project right click on the project, then select Properties, Build Events, Post Build Event Command line

### WinRTComponent

A simple C++ WinRT Component with a class returning a string

* The component is written using [C++/WinRT](https://docs.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/intro-to-using-cpp-with-winrt) instead of [C++/CX](https://docs.microsoft.com/en-us/cpp/cppcx/visual-c-language-reference-c-cx?view=vs-2017). Therefore, it requires an installed Nuget Package: [Microsoft.Windows.CppWinRT](https://www.nuget.org/packages/Microsoft.Windows.CppWinRT/).
* To manage the specific C++ Runtime Dependencies of the WinRT component, the app uses the [Microsoft.VCRTForwarders.140](https://aka.ms/vcrtfwdnuget) NuGet package.

### Building and running the sample

1. Load the Project solution.
2. Retarget the solution to the SDK version on your machine: Right click, Retarget solution
3. Build the WinRTComponent project.
4. Build the CSharpConsoleApp project
5. Run the app