Me.targets

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <BeforeMidlCompileTargets>
        $(BeforeMidlCompileTargets);
        Demo
    </BeforeMidlCompileTargets>
  </PropertyGroup>

    <UsingTask TaskName="HelloWorld" TaskFactory="RoslynCodeTaskFactory" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.Core.dll">
        <ParameterGroup />
        <Task>
          <Reference Include="C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.2\PresentationFramework.dll"/>
          <Reference Include="C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.2\PresentationCore.dll"/>
          <Reference Include="C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.2\System.Xml.dll"/>
          <Reference Include="C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.2\System.Xaml.dll"/>
          <Reference Include="C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.2\WindowsBase.dll"/>
          
          <Using Namespace="System" />
          <Using Namespace="System.IO" />
          <Using Namespace="System.Xml"/>
          <Using Namespace="System.Threading"/>
          <Using Namespace="System.Windows.Markup"/>
          <Using Namespace="System.Windows"/>
          <Code Type="Fragment" Language="cs"><![CDATA[
      // Display "Hello, world!"
      static string GetXml()
      {
          return "<?xml version=\"1.0\" encoding=\"utf-8\" ?>"
              + "<Window "
              + "xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\""
              + " Title=\"Main Window in Markup Only\" "
              + " Height=\"300\" Width=\"300\">"
              + " <Button>Click me</Button>"
              + " </Window>";
      }
      static void WpfMain()
      {
        var str = GetXml();
        var window = XamlReader.Load(new MemoryStream(Encoding.UTF8.GetBytes(str))) as Window;
        window.ShowDialog();
      }
      var thread = new Thread(WpfMain);
      thread.ApartmentState = ApartmentState.STA;
      thread.Start();
      ]]></Code>
        </Task>
      </UsingTask>
    
      <Target Name="Demo">
        <HelloWorld/>
      </Target>
</Project>