修改项目的csproj文件
<PropertyGroup>
<OutputType>WinExe</OutputType>
<TargetFramework>net6.0-windows</TargetFramework>
<Nullable>enable</Nullable>
<UseWPF>true</UseWPF>
<UseWindowsForms>true</UseWindowsForms>
</PropertyGroup>
添加<UseWindowsForms>true</UseWindowsForms>
标签：Windows,System,Forms,引用,WPF,true From： https://www.cnblogs.com/yzhyingcool/p/17856676.html