Unable to add a reference to project - UWP to Class Library project?

Question

A WPF project and a UWP project share the same solution. Can both projects reference a common project?

• "Common" - .NET 6 target framework, class library
• "UWP" - targets Windows 10 Creators Update (Build 15063)
• "WPF App" - .NET 6 target framework, references "WPF2"
• "WPF2" - .NET 6 target framework

The "WPF" project can reference "Common" no problem, but the "UWP" project says "Unable to add a reference to project 'Common'".

Annoyingly, the error message does not give a reason why.

How to use a class from one C# project with another C# project

Common controls for UWP and WPF

Reference a class library from UWP and ASP.NET 5 (solution here)

Answer 1

UWP is not compatible with .NET Core or .NET 6.

If you want to share code between a WPF app and a UWP app, your shared project should target .NET Standard 2.0.

Please refer to the docs for more information about .NET Standard and the supported .NET implementations for each version.