Exception on Windows 7

[dmitry-shechtman]

I'm getting the following exception on Windows 7:

System.TypeLoadException: Could not find Windows Runtime type 'Windows.Data.Xml.Dom.XmlDocument'. ---> System.PlatformNotSupportedException: Operation is not supported on this platform.
   --- End of inner exception stack trace ---
   at DesktopToast.ToastManager.<ShowAsync>d__0.MoveNext()
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.Start[TStateMachine](TStateMachine& stateMachine)
   at DesktopToast.ToastManager.ShowAsync(ToastRequest request)