Winforms/WPF .NET9.0 app cannot be ran on Windows 10 20H2(OS build 19042.2965)

[Olina-Zhang]

Describe the bug

Winforms/WPF .NET9.0 app cannot be ran on Windows 10 20H2(OS build 19042.2965) and Windows 10 21H1, but .NET 8.0 apps work well

To Reproduce

1. Install the latest .NET 9.0 RC2 SDK build from: https://github.com/dotnet/sdk/blob/main/documentation/package-table.md

2. Create a Winforms application by CLI
   

3. Build and run created Winforms application by CLI

Actual result: dotnet build successfully, but dotnet run failed with nonsense characters output, Winforms runtime doesn't display

[KalleOlaviNiemitalo]

https://learn.microsoft.com/en-us/lifecycle/products/windows-10-enterprise-and-education shows support for Windows 10 Enterprise version 20H2 ended on May 9, 2023.

https://learn.microsoft.com/en-us/dotnet/core/install/windows#supported-versions says .NET is not supported on end-of-life versions of Windows.

[Tanya-Solyanik]

@Olina-Zhang - are you sure this is specific to Windows 10 20H2(OS build 19042.2965)? Otherwise it looks like a dupe of dotnet/msbuild#10579

[KalleOlaviNiemitalo]

The screen shot shows a "Faulting application" error in the Application event log. dotnet/msbuild#10579 would not cause that.

[Olina-Zhang]

@Tanya-Solyanik Today I verified more Windows versions, It also reproes in Windows 10 21H1, but not Windows 10 21H2 and above. This issue is about created Winforms/WPF apps cannot be ran.

[baronfel]

@merriemcgaw are there any known issues with Windows 10 21H1?

[merriemcgaw]

With Win10 21H1 in general or with WinForms? I think this issue is the one report I've seen for WinForms.
@Olina-Zhang has your team encountered any other issues? Does the .NET version you try make a difference here?

[Olina-Zhang]

@merriemcgaw this issue is about Winforms/WPF app failed to use CLI dotnet run for created .NET 9.0 apps on only Windows 10 20H2 and 21H1, we cannot see runtime form displayed, but for .NET 8 works well. Now we cannot find OS image in Azure portal to create these machines to verify the incoming .NET 9.0 GA build, because these 2 OSes are out of support.

[merriemcgaw]

@jamshedd are we supporting Win10 20H2, correct? In that case I'd think we can close this issue. I wouldn't want to spend much resources trying to diagnose for an OS we actively don't support.

[snintendog]

On 21H2 can confirm .net 9.0.101 wont work on it now. Major incompatibility.

[hxmcn]

I can confirm that .net WPF application target to .net 9 and .net 10 preview can not run on windows 22H2 (10.0.19045.2908), run the application does not show the main window and the process silently shutdown after a few seconds.
Downgrade to .net 8 can run on the same PC.
This is a very serious bug!