WindowsFormsApplication1.csproj

<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
  <PropertyGroup>
      <TargetFramework>netcoreapp3.0</TargetFramework>
      <UseWindowsForms>true</UseWindowsForms>
      <OutputType>WinExe</OutputType>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="OxyPlot.WindowsForms" Version="2.0.0" />
  </ItemGroup>
</Project>