在 BaseCommand 中，将 CanExecuteChanged 替换为以下内容。

Inside BaseCommand, replace the CanExecuteChanged to look like the following. And it will work the way you want it.

   public event EventHandler CanExecuteChanged
    {
        add
        {
            CommandManager.RequerySuggested += value;
        }
        remove
        {
            CommandManager.RequerySuggested -= value;
        }
    }