How can I add System.Windows.Forms to WPF application when adding via reference/Depenency doesn't work?

Question

Following every guide everywhere:

• Step 1:

• Step 2: it works! Huzzah! Except that it doesn't. Instead I get yellow triangles:

This project is tiny for now because I only just started. The guides about yellow triangles talk about conflicts which can't be the case here. I have next to nothing imported or used yet:

Answer 1

Apparently this is due to using .Net Core and Microsoft couldn't anticipate that people would want to use forms in the new normal...

I found this: How to use System.Windows.Forms in .NET Core class library

This is what worked:

• Removed reference/dependancy entirely
• Right-click project, Unload
• Right-click project, Edit project file
• Add the following:

    <PropertyGroup>
        <TargetFramework>net6.0-windows</TargetFramework>
        <UseWPF>true</UseWPF>
        <UseWindowsForms>true</UseWindowsForms>
    </PropertyGroup>

• Reload project file
• Add "using system.windows.forms" to the top.