<Project Sdk="Microsoft.NET.Sdk"> <PropertyGroup> <OutputType>WinExe</OutputType> <TargetFrameworks>net20;net45;net5.0-windows</TargetFrameworks> <UseWindowsForms>true</UseWindowsForms> <RootNamespace>MBox</RootNamespace> </PropertyGroup> <ItemGroup> <Reference Include="System.Windows.Forms" /> </ItemGroup> </Project>