WPF自定义ICommand实现和CanExecuteChanged事件

只需执行 CanExecuteChanged 事件如下:

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

将命令分配给控件时,它将订阅 已更改CanExecuteChanged 事件。如果你把它“重定向”到 CommandManager.RequerySuggested 事件,控件将在 命令管理器请求建议 被触发。

我非常喜欢使用prism的delegatecommand实现来绑定viewModel。( http://msdn.microsoft.com/en-us/library/ff654132.aspx )您可以通过对每个命令调用器调用raiseCanExecute()。

简单用法示例:

public class ViewModel
{
   public ViewModel()
   {
      Command = new DelegateCommand<object>(x => CommandAction(), x => CanCommandAction());
   }

   bool state;

   public void ChangeState(bool value)
   {
      state = value;
      Command.RaiseCanExecuteChanged();
   }

   public DelegateCommand<object> Command {get; private set;}

   private void CommandAction()
   {
      //do smthn
   }

   private bool CanCommandAction() { return true == state; }
}

//and binding as usual
Command="{Binding Command}"