获取路由事件的源Source和OriginalSource

路由事件的消息包含在RoutedEventArgs实例中，该实例有两个属性Source和OriginalSource，都是表示路由事件传递的起点，即事件消息的源头，只不过Source表示的是LogicalTree上的消息源头，而OriginalSource表示的是VisualTree上的源头。

主要代码如下：

public MainWindow()
{
    InitializeComponent();
    this.AddHandler(Button.ClickEvent, new RoutedEventHandler(this.ButtonClicked));
}

void ButtonClicked(object sender, RoutedEventArgs e)
{
    string SourceString = string.Format("LogicalTree start point: {0}, type is {1}",
        (e.Source as FrameworkElement).Name, e.Source.GetType().Name);
    string OriginalSourceString = string.Format("VisualTree start point: {0}, type is {1}",
        (e.OriginalSource as FrameworkElement).Name, e.OriginalSource.GetType().Name);

    MessageBox.Show(OriginalSourceString + "\r\n" + SourceString);
}

获取路由事件的源Source和OriginalSource