WPF 微软官网 自定义路由事件 ，有一段代码不懂，求解答

Question

WPF 微软官网 自定义路由事件 ，有一段代码不懂，以下为源代码

public class CustomButton : Button
{
    // Register a custom routed event using the Bubble routing strategy.
    public static readonly RoutedEvent ConditionalClickEvent = EventManager.RegisterRoutedEvent(
        name: "ConditionalClick",
        routingStrategy: RoutingStrategy.Bubble,
        handlerType: typeof(RoutedEventHandler),
        ownerType: typeof(CustomButton));

    // Provide CLR accessors for assigning an event handler.
    public event RoutedEventHandler ConditionalClick
    {
        add { AddHandler(ConditionalClickEvent, value); }
        remove { RemoveHandler(ConditionalClickEvent, value); }
    }

    void RaiseCustomRoutedEvent()
    {
        // Create a RoutedEventArgs instance.
        RoutedEventArgs routedEventArgs = new(routedEvent: ConditionalClickEvent);

        // Raise the event, which will bubble up through the element tree.
        RaiseEvent(routedEventArgs);
    }

    // For demo purposes, we use the Click event as a trigger.
    protected override void OnClick()
    {
        // Some condition combined with the Click event will trigger the ConditionalClick event.
        if (DateTime.Now > new DateTime())
            RaiseCustomRoutedEvent();

        // Call the base class OnClick() method so Click event subscribers are notified.
        base.OnClick();
    }
}
public class CustomButton : Button
{
    // Register a custom routed event using the Bubble routing strategy.
    public static readonly RoutedEvent ConditionalClickEvent = EventManager.RegisterRoutedEvent(
        name: "ConditionalClick",
        routingStrategy: RoutingStrategy.Bubble,
        handlerType: typeof(RoutedEventHandler),
        ownerType: typeof(CustomButton));

    // Provide CLR accessors for assigning an event handler.
    public event RoutedEventHandler ConditionalClick
    {
        add { AddHandler(ConditionalClickEvent, value); }
        remove { RemoveHandler(ConditionalClickEvent, value); }
    }

    void RaiseCustomRoutedEvent()
    {
        // Create a RoutedEventArgs instance.
        RoutedEventArgs routedEventArgs = new(routedEvent: ConditionalClickEvent);

        // Raise the event, which will bubble up through the element tree.
        RaiseEvent(routedEventArgs);
    }

    // For demo purposes, we use the Click event as a trigger.
    protected override void OnClick()
    {
        // Some condition combined with the Click event will trigger the ConditionalClick event.
        if (DateTime.Now > new DateTime())
            RaiseCustomRoutedEvent();

        // Call the base class OnClick() method so Click event subscribers are notified.
        base.OnClick();
    }
}

// The ConditionalClick event handler.
private void Handler_ConditionalClick(object sender, RoutedEventArgs e)
{
    string senderName = ((FrameworkElement)sender).Name;
    string sourceName = ((FrameworkElement)e.Source).Name;

    Debug.WriteLine($"Routed event handler attached to {senderName}, " +
        $"triggered by the ConditionalClick routed event raised on {sourceName}.");
}

// Debug output when CustomButton is clicked:
// Routed event handler attached to CustomButton,
//     triggered by the ConditionalClick routed event raised on CustomButton.
// Routed event handler attached to StackPanel1,
//     triggered by the ConditionalClick routed event raised on CustomButton.

<Window x:Class="CodeSample.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:custom="clr-namespace:WpfControl;assembly=WpfControlLibrary"
        Title="How to create a custom routed event" Height="100" Width="300">

    <StackPanel Name="StackPanel1" custom:CustomButton.ConditionalClick="Handler_ConditionalClick">
        <custom:CustomButton
            Name="customButton"
            ConditionalClick="Handler_ConditionalClick"
            Content="Click to trigger a custom routed event"
            Background="LightGray">
        </custom:CustomButton>
    </StackPanel>
</Window>

问题:StackPanel Name="StackPanel1" custom:CustomButton.ConditionalClick="Handler_ConditionalClick" 这一段代码，ConditionalClick 不属于StackPanel 里面的东西，它怎么能被添加到StackPanel 里面呢？
谢谢！

Answer 1

看不懂的那一段，其实相当于 在后台代码写
this.StackPanel1.AddHandler(CustomButton .ConditionalClickEvent , new RoutedEventHandler(Handler_ConditionalClick));

StackPanel 有这样一个方法，为这个StackPanel1一个路由事件，在StackPanel1中用xaml中写法就是
custom:CustomButton.ConditionalClick="Handler_ConditionalClick" 和上面的后台代码是等价的
这里需要注意的是：虽然StackPanel1附加了一个ConditionalClick事件，但是并不等于StackPanel1就具有了ConditionalClick
事件，只是将这个事件附加给了StackPanel1，让StackPanel1可以监听到CustomButton的ConditionalClick事件。

参考：https://blog.csdn.net/qq_39847278/article/details/128050213