You need to expose a property that will represent the image URI and ensure it notifies the UI when it changes.

1. Add HeldPieceImageUri as a property with INotifyPropertyChanged to ensure the UI updates when the image changes.

   2. Use another function UpdateHeldPieceImage() to update HeldPieceImageUri based on the top value of holdStack.
   3. Finally, call UpdateHeldPieceImage() at the end of holdTetromino().

Don’t forget to update your WPF XAML to include an Image control to preview the held piece. Also make sure the TetrisViewModel is set as the DataContext of your Window.