Can't reference WinRT component project from a WinUI 3 C# app

[jaigak]

Referencing a native WinRT component project created using the old templates doesn't work from a WinUI 3 app as the build system tries to reference the output WinMD instead of invoking CsWinRT even though I'm just using a ProjectReference. The project does have the Windows Desktop compatible option enabled. This problem only occurs in C# apps, C++ projects work fine.

[angelazhangmsft]

@Jaiganeshkumaran, I assume you are trying to reference a C++/WinRT component from a C# app? In order to do this, you will need to explicitly invoke CsWinRT to generate the C# projection for your component. Here is an example: https://docs.microsoft.com/windows/uwp/csharp-winrt/net-projection-from-cppwinrt-component

If you are consuming the component with a ProjectReference, you currently need to reference the Microsoft.Windows.CsWinRT package in your app in order to workaround the winmd reference (In .NET 5+, the built-in winmd support was removed).