wpf Command

//基本的ICommand

 public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            clearCmd clcmd = new clearCmd(tb);
            bt.Command = clcmd;
          
        }
    
    public class clearCmd : ICommand
    {
        TextBox data;
        public clearCmd(TextBox o)
        {
            data = o;
        }
        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }

        public bool CanExecute(object parameter)
        {
            return !string.IsNullOrEmpty(data.Text);
        }

        public void Execute(object parameter)
        {
            data.Clear();
        }
    }

//路由命令RoutedCommand，本身不包含CanExecute和Executed实际执行逻辑，而是引发逻辑树遍历，查找绑定了了该路由命令的CommandBinding,由CommandBinding实际执行CanExecute和Executed。

public partial class MainWindow : Window
    {
        private RoutedCommand clearCmd = new RoutedCommand("Clear", typeof(MainWindow));
        public MainWindow()
        {
            InitializeComponent();
            bt.Command = clearCmd;
            clearCmd.InputGestures.Add(new KeyGesture(Key.C, ModifierKeys.Alt)); //这是为命令增加快捷键
            bt.CommandTarget = tb;//这里为逻辑树遍历起点
            CommandBinding cb = new CommandBinding();
            cb.Command = clearCmd;
            cb.CanExecute += Cb_CanExecute;
            cb.Executed += Cb_Executed;
            this.CommandBindings.Add(cb);
        }

        private void Cb_Executed(object sender, ExecutedRoutedEventArgs e)
        {
            tb.Text = "";
            e.Handled = true;
        }

        private void Cb_CanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            e.CanExecute = !string.IsNullOrEmpty(tb.Text);
            e.Handled = true;
        }
    }