从 Unloaded 事件处理程序引发的 RoutedEvent 不冒泡

Question

我有一个继承自 ItemsControl 的自定义用户控件。通过它的 ItemTemplate，它从 ObservableCollection 为每个附加的 ViewModel 创建一个 ChildControl。

public class ChildControl : FrameworkElement
{
    public static readonly RoutedEvent CreatedEvent = EventManager.RegisterRoutedEvent(
        nameof(Created),
        RoutingStrategy.Bubble,
        typeof(RoutedEventHandler),
        typeof(ChildControl));

    public static readonly RoutedEvent RemovedEvent = EventManager.RegisterRoutedEvent(
        nameof(Removed),
        RoutingStrategy.Bubble,
        typeof(RoutedEventHandler),
        typeof(ChildControl));

    public ChildControl
    {
        Loaded += OnLoaded;
        Unloaded += OnUnloaded;
    }

    public event RoutedEventHandler Created
    {
        add => AddHandler(CreatedEvent, value);
        remove => RemoveHandler(CreatedEvent, value);
    }

    public event RoutedEventHandler Removed
    {
        add => AddHandler(RemovedEvent, value);
        remove => RemoveHandler(RemovedEvent, value);
    }

    private void OnLoaded(object sender, RoutedEventArgs e)
    {
        RaiseEvent(new RoutedEventArgs(CreatedEvent));
    }

    private void OnUnloaded(object sender, RoutedEventArgs e)
    {
        RaiseEvent(new RoutedEventArgs(RemovedEvent));
    }
}

和 CustomItemsControl

public class CustomItemsControl : ItemsControl
{
    public CustomItemsControl()
    {
        AddHandler(ChildControl.CreatedEvent, new RoutedEventHandler(OnCreatedEvent));
        AddHandler(ChildControl.RemovedEvent, new RoutedEventHandler(OnRemovedEvent));
    }
    
    private void OnCreatedEvent(object sender, RoutedEventArgs e)
    {
        // stuff
    }

    private void OnRemovedEvent(object sender, RoutedEventArgs e)
    {
        // stuff
    }
}

除了 RemovedEvent 处理程序之外，一切正常。当事件在 ChildControl 的 Unloaded 事件处理程序中引发时，它不会被 CustomItemsControl 捕获。但是，当调用 RemovedEvent 时，假设在 Loaded 事件处理程序中，它会被 CustomItemsControl 捕获。所以证明一切正常。

我是不是做错了什么，或者这是否意味着从 Unloaded 事件处理程序中调用的 RoutedEvents 没有按设计冒泡？

Answer 1

东西没了

但你还是希望听到它。

Re-consider 卸载事件。想想发生了什么。

“当元素从加载元素的元素树中移除时发生。”

https://docs.microsoft.com/en-us/dotnet/api/system.windows.frameworkelement.unloaded?view=netcore-3.1https://docs.microsoft.com/en-us/dotnet/api/system.windows.frameworkelement.unloaded?view=netcore-3.1

没了

因为没有。

不在任何视觉树中，不在任何东西中。

因为它是从UI.

卸载的

来自它的路由事件不能冒泡或隧道或任何涉及可视化树的事件。因为 ui 元素不再在那棵树中。

您需要做的是首先引发自定义路由事件，然后卸载您的控件。也许完全使用不同的方法会是更好的方法。示例包括：prism eventaggregator 或 mvvmlight messenger 或将引用从父级传递给子级以便它可以直接调用方法。

从 Unloaded 事件处理程序引发的 RoutedEvent 不冒泡

RoutedEvent raised from Unloaded event handler not bubbling

c#

wpf

itemscontrol

routed-events