How to show message box on .net core Console application?

Question

I'm developing .net core console application. I want to alert to user when want to exit application. Like below;

 MessageBox.Show("Contiue or not", "Question", MessageBoxButtons.YesNo, MessageBoxIcon.None, MessageBoxDefaultButton.Button1) == DialogResult.No)
    Application.Exit();

But I can't add System.Windows.Forms referance to the my project. I'm getting this error.

 Error  CS0234  The type or namespace name 'Forms' does not exist in the namespace 'System.Windows' (are you missing an assembly reference?)    

Is that possible to show Message Box on .net core Console Application?

Answer 1

In order to use Windows Forms you need to modify .csproj:

• set UseWindowsForms to true
• append -windows to TargetFramework (e.g. net6.0-windows)

ConsoleApp.csproj:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0-windows</TargetFramework>
    <UseWindowsForms>true</UseWindowsForms>
  </PropertyGroup>
</Project>

Program.cs:

System.Console.WriteLine("Hello, Console!");
System.Windows.Forms.MessageBox.Show("Hello, Popup!");

Result:

Notes:

• I checked this solution on .NET Core 3.1, .NET 5 and .NET 6 on Windows x64.
• If you don't want console window to be shown, set OutputType in .csproj to WinExe instead of Exe.
• Windows Forms works only on Windows, so as this solution.
• On .NET Core 3.1 there is no requirement to change target framework to Windows, however it is still impossible to publish executable for Linux OS.
• If you need cross-platform solution that shows popups on Windows and only use console on Linux – you can create custom build configuration and use preprocessor directives as in the example below.

Cross-platform ConsoleApp.csproj:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <Configurations>Debug;Release;WindowsDebug;WindowsRelease</Configurations>
  </PropertyGroup>
  <PropertyGroup Condition="'$(Configuration)' == 'WindowsDebug' Or '$(Configuration)' == 'WindowsRelease'">
    <DefineConstants>WindowsRuntime</DefineConstants>
    <TargetFramework>net6.0-windows</TargetFramework>
    <UseWindowsForms>true</UseWindowsForms>
  </PropertyGroup>
</Project>

Cross-platform Program.cs

System.Console.WriteLine("Hello, Console!");

#if WindowsRuntime
System.Windows.Forms.MessageBox.Show("Hello, Popup!");
#endif