//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;        }    }