AGENT.PackageViewer.Command.CommandReference.OnCommandChanged C# (CSharp) Method

        private static void OnCommandChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            CommandReference commandReference = (CommandReference)d;
            ICommand oldCommand = e.OldValue as ICommand;
            ICommand newCommand = e.NewValue as ICommand;

            if (oldCommand != null)
            {
                oldCommand.CanExecuteChanged -= commandReference.CanExecuteChanged;
            }
            if (newCommand != null)
            {
                newCommand.CanExecuteChanged += commandReference.CanExecuteChanged;
            }
        }