C# WPF 路由事件介绍

 为什么会有两种情况，刚接触的可能有这样的疑问。

ValueText.PreviewMouseWheel += mouseAngleChange;

UpButton.AddHandler(Button.MouseLeftButtonDownEvent, new MouseButtonEventHandler(UpButton_MouseDown), true);

为什么用下边的写法就出现错误：error CS0176: 无法使用实例引用访问成员"System.Windows.UIElement.MouseLeftButtonDownEvent。

UpButton.MouseLeftButtonDownEvent += UpButton_MouseDown;

 这里需要看定义，可以看出他们一个是静态成员，一个不是静态成员，所以MouseLeftButtonDownEvent只能由类Button直接调用，不能由实例化的UpButton调用。

public event MouseWheelEventHandler PreviewMouseWheel; 

public static readonly RoutedEvent MouseLeftButtonDownEvent;

///

WPF 路由事件(RoutedEventArgs 事件消息、 RoutedEvent 路由事件、RoutedEventHandler路由事件处理程序、RaiseEvent引发路由事件)

https://blog.youkuaiyun.com/litao2/article/details/54947009这篇文章讲的非常好。

自定义路由事件：

//定义路由事件
        public static readonly RoutedEvent AngleChangeEvent =
            EventManager.RegisterRoutedEvent("AngleChange", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(ServoView));

        public event RoutedEventHandler AngleChange
        {
            add
            {
                this.AddHandler(AngleChangeEvent, value);
            }

            remove
            {
                this.RemoveHandler(AngleChangeEvent, value);
            }
        }

        public void OnAngleChange(double value)//角度变化，将该信息发送出去，MainWindow的servosView侦听了该事件
        {
            this.curAngle = value;
            servoAngleSlider.Value = value;
            RoutedEventArgs arg = new RoutedEventArgs(AngleChangeEvent, this);

            this.RaiseEvent(arg);
        }

 这里就可以通过该方法增加事件的实现。

servosViewList[i].AddHandler(ServoView.AngleChangeEvent, new RoutedEventHandler(this.angleChangeHandler));

这里是一个例子。转的https://blog.youkuaiyun.com/litao2/article/details/54947009

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
 
namespace WpfApplication
{
    /// <summary>
    /// Window6.xaml 的交互逻辑
    /// </summary>
    public partial class Window6 : Window
    {
        public Window6()
        {
            InitializeComponent();
            //事件、委托指向方法
            mybutton.Open+=new RoutedEventHandler(mybutton_Open);
        }
 
        public void mybutton_Open(object sender, RoutedEventArgs e)
        {
            MessageBox.Show("打开");
        }
    }
 
    class MyButton : Button
    { 
        //第一步：声明并注册【路由事件】
        //EventManager.RegisterRoutedEvent(CLR事件包装器名称,路由事件冒泡策略,
//事件处理程序的类型,路由事件的所有者类类型)
        public static readonly RoutedEvent OpenEvent = EventManager.RegisterRoutedEvent
            ("Open",RoutingStrategy.Bubble,typeof(RoutedEventHandler),typeof(MyButton));
 
        //第二步：为路由事件添加CLR事件包装器
        public event RoutedEventHandler Open
        {
            add { this.AddHandler(OpenEvent, value); }
            remove { this.RemoveHandler(OpenEvent, value); }
        }
 
        //第三步：激发路由事件
        protected override void OnClick()
        {
            base.OnClick();
            //创建事件携带信息（RoutedEventArgs类实例）,并和路由事件关联
            RoutedEventArgs args = new RoutedEventArgs(OpenEvent,this);
            //调用元素的RaiseEvent方法（继承自UIElement类），将事件发出去
            this.RaiseEvent(args);
        }
    }
}


<Window x:Class="WpfApplication.Window6"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication"
        Title="Window6" Height="300" Width="300">
    <Grid>
        <local:MyButton Content="测试" x:Name="mybutton"/>
    </Grid>
</Window>

这里对这个例子进行修改

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace test2
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            //事件、委托指向方法
            mybutton.Open += new RoutedEventHandler(mybutton_Open);
            mybutton.AddHandler(MyButton.OpenEvent,new RoutedEventHandler(this.mybutton_Open1));
            mybutton.AddHandler(MyButton.OpenEvent, new RoutedEventHandler(this.mybutton_Open1));
            mybutton.AddHandler(MyButton.OpenEvent, new RoutedEventHandler(this.mybutton_Open1));

        }

        public void mybutton_Open(object sender, RoutedEventArgs e)
        {
            MessageBox.Show("打开");
        }
        public void mybutton_Open1(object sender, RoutedEventArgs e)
        {
            MessageBox.Show("关闭");
        }
    }

    class MyButton : Button
    { 
        //第一步：声明并注册【路由事件】
        //EventManager.RegisterRoutedEvent(CLR事件包装器名称,路由事件冒泡策略,
//事件处理程序的类型,路由事件的所有者类类型)
        public static readonly RoutedEvent OpenEvent = EventManager.RegisterRoutedEvent
            ("Open",RoutingStrategy.Bubble,typeof(RoutedEventHandler),typeof(MyButton));
 
        //第二步：为路由事件添加CLR事件包装器
        public event RoutedEventHandler Open
        {
            add { this.AddHandler(OpenEvent, value); }
            remove { this.RemoveHandler(OpenEvent, value); }
        }
 
        //第三步：激发路由事件
        protected override void OnClick()
        {
            base.OnClick();
            //创建事件携带信息（RoutedEventArgs类实例）,并和路由事件关联
            RoutedEventArgs args = new RoutedEventArgs(OpenEvent,this);
            //调用元素的RaiseEvent方法（继承自UIElement类），将事件发出去
            this.RaiseEvent(args);
        }
    }

}


<Window x:Class="test2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:test2"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <local:MyButton Content="测试" x:Name="mybutton"/>
    </Grid>
</Window>

可以知道这里用

mybutton.Open += new RoutedEventHandler(mybutton_Open);
mybutton.AddHandler(MyButton.OpenEvent,new RoutedEventHandler(this.mybutton_Open1));

这两种方法都可以实现路由事件的添加，正如文章最开始讨论的问题那样，只不过是两种不同的方式。

mybutton.AddHandler(MyButton.OpenEvent,new RoutedEventHandler(this.mybutton_Open1));
 mybutton.AddHandler(MyButton.OpenEvent, new RoutedEventHandler(this.mybutton_Open1));
 mybutton.AddHandler(MyButton.OpenEvent, new RoutedEventHandler(this.mybutton_Open1));

这里连续写三次，则程序会连续的执行三次该路由事件。

具体程序已经贴出，如果有问题的，可以参考这里https://download.youkuaiyun.com/download/yanxiaoyunsana/10975277。