Console output no longer working dotnet run and UseWindowsForms

[sipsorcery]

Description

For console applications that need to display a Windows Form executing the project with dotnet run displayed Console.Write* output in the same manner as a standard console application.

With .NET SDK (5.0.100-preview.8.20417.9) console output is no longer displayed.

If the program is built with Visual Studio and then run from directly from the .exe, with the Visual Studio debugger or with dotnet run --no-build then console output works properly.

If the program is build and run with dotnet run console output does not appear.

Configuration

.NET SDK (5.0.100-preview.8.20417.9)
Microsoft Windows 10 Pro 10.0.19041 Build 19041
x64

Other information

Minimal project and program file to replicate:

<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <UseWindowsForms>true</UseWindowsForms>
  </PropertyGroup>

</Project>

using System;

class Program
{
    [STAThread]
    static void Main(string[] args)
    {
        Console.WriteLine("Hello World!");
    }
}

• Build and execute with dotnet run will not display anything on the console.
• Rebuild with Visual Studio and execute with dotnet run --no-build will display console output.
• Build and execute again with dotnet run will not display anything on the console.

Tagging subscribers to this area: @eiriktsarpalis, @jeffhandley
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[jeffhandley]

With .NET SDK (5.0.100-preview.8.20417.9) console output is no longer displayed.

@sipsorcery Thanks for reporting this. With your statement that "output is no longer displayed," does that imply that you saw this working with a previous version and is therefore a regression in 5.0?

[sipsorcery]

does that imply that you saw this working with a previous version and is therefore a regression in 5.0?

Yes. I was definitely getting normal console output on this type of mixed console/forms application up until very recently.

I spent some more time trying to find a combination of dotnet run with --framework and/or --runtime that would work but to no avail. The best I can get is to build with the Visual Studio 2019 IDE and then use --no-build.

dotnet run --no-build
Hello World!

[adamsitnik]

I suspect that it is a by-design change in WinForms 5.0.

@JeremyKuhne do you happen to know if writing to console has been disabled in WinForms for .NET 5?

[JeremyKuhne]

do you happen to know if writing to console has been disabled in WinForms for .NET 5?

Nothing was done in WinForms afaik, nor would we explicitly want to remove said functionality. This should be below the WinForms level.

[jkotas]

This is duplicate of dotnet/sdk#13331. dotnet/sdk#13331 (comment) describes workaround you can use to get to the old behavior.