protected virtual void SetWindowViewModel(WindowViewModel WindowViewModel)
 {
     if (WindowViewModel == null)
         return;
     WindowViewModel.Owner = this;
     WindowViewModel.RequestClose += OnRequestClose;
 }
 protected virtual void ClearWindowViewModel(WindowViewModel WindowViewModel)
 {
     if (WindowViewModel == null)
         return;
     WindowViewModel.RequestClose -= OnRequestClose;
     WindowViewModel.Owner = null;
 }