无法将程序集引用添加到控制台应用程序

Question

Currently I'm unable to add an assembly reference to my C# project in Visual Studio 2019.

I don't know if this is an error with Visual Studio itself or it's my fault.

Currently my References page looks like this:

If I try to add a COM Reference then I get the following error of:

Severity    Code    Description Project File    Line    Suppression State
Warning MSB3290 Failed to create the wrapper assembly for type library "{215d64d2-031c-33c7-96e3- 
61794cd1ee61}". Type library 'System_Windows_Forms' was exported from a CLR assembly and cannot be 
re-imported as a CLR assembly.  MyProgram   C:\Program Files (x86)\Microsoft Visual 
Studio\2019\Community\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets   2705    

All I want is to add a reference to Windows Forms.

Answer 1

Reference to a type library would indcate you are adding a COM reference.

But System.Windows.Forms is a .NET assembly, so you should be selecting it from the Assemblies list on the references manager (shown when you add reference).

If this is a .NET Core project then add the appropriate reference via NuGet (in project's context menu in solution explorer). But it also needs the right SDK version.

Probably easier to copy from a fresh WinForms project created from the VS New Project and see what NuGet references it included.

Correction

For .NET Core 3.1 you don't need any references for the WinForms assemblies. Instead you need the right settings in your .csproj :

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

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

</Project>

Answer 2

There could possibly because of you are trying to refer a COM library build on different architecture than the project you want to get the COM reference. For example COM lib may be built on x64 and your project may be built upon x32.

Or will you please elaborate your issue or help me on how to reproduce it.