整理：WPF中应用附加事件制作可以绑定命令的其他事件

原文:整理：WPF中应用附加事件制作可以绑定命令的其他事件

目的：应用附加事件的方式定义可以绑定的事件，如MouseLeftButton、MouseDouble等等

一、定义属于Control的附加事件ControlAttachEvent类

/// <summary> 附加事件 </summary>





    public static class ControlAttachEvent





    {





 





        #region - 双击事件 -





 





        public static readonly DependencyProperty PreviewMouseDoubleClickProperty =





            DependencyProperty.RegisterAttached("PreviewMouseDoubleClick", typeof(ICommand), typeof(ControlAttachEvent), new FrameworkPropertyMetadata(OnCommandChanged));





 





        public static ICommand GetPreviewMouseDoubleClick(Control target)





        {





            return (ICommand)target.GetValue(PreviewMouseDoubleClickProperty);





        }





 





        public static void SetPreviewMouseDoubleClick(Control target, ICommand value)





        {





            target.SetValue(PreviewMouseDoubleClickProperty, value);





        }





 





        private static void Element_PreviewMouseDoubleClick(object sender, MouseButtonEventArgs e)





        {





            Control control = sender as Control;





 





            ICommand command = GetPreviewMouseDoubleClick(control);





            





            if (command.CanExecute(sender))





            {





                command.Execute(sender);





                e.Handled = true;





            }





        }





 





        private static void OnCommandChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)





        {





            Control control = d as Control;





 





            control.PreviewMouseDoubleClick += new MouseButtonEventHandler(Element_PreviewMouseDoubleClick);





        }





        #endregion





 





        public static DependencyProperty PreviewMouseLeftButtonDownCommandProperty = DependencyProperty.RegisterAttached("PreviewMouseLeftButtonDown",typeof(ICommand),typeof(ControlAttachEvent),new FrameworkPropertyMetadata(null, new PropertyChangedCallback(PreviewMouseLeftButtonDownChanged)));





 





        public static void SetPreviewMouseLeftButtonDown(DependencyObject target, ICommand value)





        {





            target.SetValue(PreviewMouseLeftButtonDownCommandProperty, value);





        }





 





        public static ICommand GetPreviewMouseLeftButtonDown(DependencyObject target)





        {





            return (ICommand)target.GetValue(PreviewMouseLeftButtonDownCommandProperty);





        }





 





        private static void PreviewMouseLeftButtonDownChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)





        {





            FrameworkElement element = target as FrameworkElement;





            if (element != null)





            {





                if ((e.NewValue != null) && (e.OldValue == null))





                {





                    element.PreviewMouseLeftButtonDown += element_PreviewMouseLeftButtonDown;





                }





                else if ((e.NewValue == null) && (e.OldValue != null))





                {





                    element.PreviewMouseLeftButtonDown -= element_PreviewMouseLeftButtonDown;





                }





            }





        }





 





        private static void element_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)





        {





            FrameworkElement element = (FrameworkElement)sender;





            ICommand command = (ICommand)element.GetValue(PreviewMouseLeftButtonDownCommandProperty);





            command.Execute(sender);





        }





    }

说明：当控件MyControl中应用该项附加事件，如注册PreviewMouseDoubleClick事件，则会触发更新方法OnCommandChanged，而在更新方法中则会注册该控件MyControl的双击事件绑定的命令，由此实现双击该控件触发绑定命令的功能；

二、调用方法

  <Button  base:ControlAttachEvent.PreviewMouseDoubleClick="{Binding RelayCommand}"/>

如上代码当双击Button时会触发ViewModel中绑定的RelayCommand命令

注：

优点在于可以把控件中不支持绑定的事件支持绑定，同时应用附加属性复用性更强

缺点在于传递事件的参数只有sender，agrs需要特殊处理,同时支持的事件与Control有关，其他更上层的控件需要单独定义