WPF 附加属性

最近在学习WPF，虽其依赖属性非常优美，而附加属性更为漂亮，以此已记之：

主要实现label双击事件

先定义所需要的附加属性

 public class MDCTest
    {
        public static DependencyProperty MouseDoubleClickCommandProperty = DependencyProperty.RegisterAttached(
            "MouseDoubleClick",
            typeof(ICommand),
            typeof(MDCTest),
            new FrameworkPropertyMetadata(null, new PropertyChangedCallback(MouseDoubleClickChanged))
            );
        public static void SetMouseDoubleClick(DependencyObject target, ICommand value)
        {
            target.SetValue(MDCTest.MouseDoubleClickCommandProperty, value);
        }
        public static ICommand GetMouseDoubleClick(DependencyObject target)
        {
            return (ICommand)target.GetValue(MDCTest.MouseDoubleClickCommandProperty);
        }
        private static void MouseDoubleClickChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)
        {
            Control control = target as Control;
            if (control != null)
            {
                if (e.NewValue != null && e.OldValue == null)
                {
                    control.MouseDoubleClick += new MouseButtonEventHandler(control_MouseDoubleClick);
                }
                else if (e.NewValue == null && e.OldValue != null)
                {
                    control.MouseDoubleClick -= new MouseButtonEventHandler(control_MouseDoubleClick);
                }
            }
        }
        public static void control_MouseDoubleClick(object sender, MouseButtonEventArgs e)
        {
            Control control = sender as Control;
            ICommand command = (ICommand)control.GetValue(MDCTest.MouseDoubleClickCommandProperty);
            command.Execute(control);
        }
    }

然后实现ICommand接口

public class RelayCommand : ICommand
    {
        private Action<object> _Execute;
        private Predicate<object> _CanExecute;

        public RelayCommand(Action<object> execte)
            : this(execte, null)
        {
        }
        public RelayCommand(Action<object> execute, Predicate<object> canExecute)
        {
            if (execute == null)
                throw new ArgumentNullException("Execute");
            _Execute = execute;
            _CanExecute = canExecute;
        }
        public bool CanExecute(object parameter)
        {
            return _CanExecute == null ? true : _CanExecute(parameter);
        }

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

        public void Execute(object parameter)
        {
            _Execute(parameter);
        }
    }

接在定义viewmodel（旨在实现这个附加属性，所以比较简单）

public class LabelViewModel
    {
        public ICommand Command
        {
            get
            {
                return new RelayCommand((m) => MessageBox.Show(m.ToString() + "command双击事件成功"));
            }
        }
    }

最后为前台显示

     <Label Name="label" local:MDCTest.MouseDoubleClick="{Binding Path=Command}">MouseDoubleClickTest</Label>