Can't debug my UWP app after tried to change language to C# 8

Question

I was happily developing and debugging my UWP app.

Project setting were: Min version 1809, Target Version 1903, Nuget Package Microsoft.NETCore.UniversalWindowsPlatform v6.1.9
Visual Studio version is VS 2019 16.3.10
OS version in my machine is 1903, complation 18362.476

until I did:

1) Tried to use a C# 8.0 language feature "default interface implementation", in VS did alt+enter and selected "Upgrade this project to C# language version 8.0"
2) Changed Minimum version from 1809 to 1903. Target version remained at 1903.
3) Updated the nuget package Microsoft.NETCore.UniversalWindowsPlatform from v6.1.9 to v6.2.9

After that, I cannot debug anymore.
At a debug attempt, Visual Studio shows me a msgbox saying "An issue in the Transition.exe process caused it to fail to activate. This process exited with a native exception"

Inspecting the debug output, it says
"The target process exited without raising a CoreCLR started event. Ensure that the target process is configured to use .NET Core. This may be expected if the target process did not run on .NET Core.
The program '[11708] Transition.exe' has exited with code -1073741701 (0xc000007b)."

I cannot debug anymore.
I tried installing the NetCore SDK version 3. Nothing happened

How do I configure my UWP app project to use .NET Core?, how do I Target a .Net Core in a UWP app? it seems like in a UWP app, you can only target an OS version, but not a framework version.
This is hell confusing. I tried to reverse the language version, but in project settings -> build -> advanced. I cannot select the language version. It says "Automatically selected based on framework version", how do I select the framework version???

What can I do?, thank you in advance.

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

C# 8 and .Net Core 3 were launched together, bringing a lot of new features.

In the documentation, you can already build WinForm and WPF programs using .Net Core 3. But for UWP applications, it is not currently supported.

Relevant development teams are working hard to bring .Net Core 3 to the Universal Windows Platform as soon as possible.

Thanks