//Show details window on button click
 private void BtnShowDetails_Click(object sender, RoutedEventArgs e)
 {
     if (dw == null)
     {
         dw = new DetailWindow(vm)
         {
             Owner = this,
             WindowStartupLocation = WindowStartupLocation.CenterOwner
         };
         dw.Closed += Dw_Closed;
         dw.Show();
     }
 }
 //On close, reset dw to null to remove window
 private void Dw_Closed(object sender, System.EventArgs e) => dw = null;