Using System.Windows.Forms in a dotnet core app

README.md

With dotnet core 3.x you can have libraries which rely on System.Windows.Forms if you setup you project file properly.

1. In the Project tag, make sure that you specify WindowsDesktop
2. Include the UseWindowsForms tag in PropertyGroup

sample.csproj

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

  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <RootNamespace>core_gdpicture</RootNamespace>
    <UseWindowsForms>true</UseWindowsForms>
    <IsPackable>false</IsPackable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="nunit" Version="3.12.0" />
    <PackageReference Include="NUnit3TestAdapter" Version="3.15.1" />
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.4.0" />
    <PackageReference Include="System.Drawing.Common" Version="4.5.1" />
    <PackageReference Include="System.Text.Encoding.CodePages" Version="4.7.1" />
    <PackageReference Include="VSI.GDIPicture.Net" Version="10.0.0.2" />
  </ItemGroup>

  <ItemGroup>
    <None Update="reo_feature_plan.pdf">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
  </ItemGroup>


</Project>