win-service-machine-dll/UPPPayDllOLD/UPPPayDll.csproj

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

  <PropertyGroup>
    <TargetFramework>net5.0-windows</TargetFramework>
    <UseWPF>true</UseWPF>
  </PropertyGroup>

  <ItemGroup>
    <Reference Include="Newtonsoft.Json">
      <HintPath>bin\Debug\net5.0-windows\Newtonsoft.Json.dll</HintPath>
    </Reference>
  </ItemGroup>

</Project>