如何删除“Button”的“Click”事件的所有事件处理程序？

Question

我有一个按钮控件，我需要删除附加到Click event的所有事件处理程序。

怎么可能？

Button button = GetButton();
button.Click.RemoveAllEventHandlers();

Answer 1

  

注意：由于我发布原始答案的问题已被关闭as a duplicate此问题，我在此处交叉发布了我的答案的改进版本。 此答案仅适用于WPF。 它不适用于Windows窗体或任何其他UI框架。

以下是一个有用的实用程序方法，用于删除订阅给定元素上的路由事件的所有事件处理程序。如果您愿意，可以将其简单地转换为扩展方法。

/// <summary>
/// Removes all event handlers subscribed to the specified routed event from the specified element.
/// </summary>
/// <param name="element">The UI element on which the routed event is defined.</param>
/// <param name="routedEvent">The routed event for which to remove the event handlers.</param>
public static void RemoveRoutedEventHandlers(UIElement element, RoutedEvent routedEvent)
{
    // Get the EventHandlersStore instance which holds event handlers for the specified element.
    // The EventHandlersStore class is declared as internal.
    var eventHandlersStoreProperty = typeof(UIElement).GetProperty(
        "EventHandlersStore", BindingFlags.Instance | BindingFlags.NonPublic);
    object eventHandlersStore = eventHandlersStoreProperty.GetValue(element, null);

    // If no event handlers are subscribed, eventHandlersStore will be null.
    // Credit: https://stackoverflow.com/a/16392387/1149773
    if (eventHandlersStore == null)
        return;

    // Invoke the GetRoutedEventHandlers method on the EventHandlersStore instance 
    // for getting an array of the subscribed event handlers.
    var getRoutedEventHandlers = eventHandlersStore.GetType().GetMethod(
        "GetRoutedEventHandlers", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
    var routedEventHandlers = (RoutedEventHandlerInfo[])getRoutedEventHandlers.Invoke(
        eventHandlersStore, new object[] { routedEvent });

    // Iteratively remove all routed event handlers from the element.
    foreach (var routedEventHandler in routedEventHandlers)
        element.RemoveHandler(routedEvent, routedEventHandler.Handler);
}

然后，您可以轻松地为按钮的Click事件调用此实用程序方法：

RemoveRoutedEventHandlers(button, Button.ClickEvent);

修改：我已经复制了bug fix implemented by corona，这样就可以在没有订阅事件处理程序时停止方法抛出NullReferenceException。信用（和赞成）应该回答他们的问题。

Answer 2

只是想略微扩展道格拉斯的常规，我非常喜欢。 我发现我需要在eventHandlersStore中添加额外的null检查来处理传递的元素还没有附加任何事件的任何情况。

/// <summary>
/// Removes all event handlers subscribed to the specified routed event from the specified element.
/// </summary>
/// <param name="element">The UI element on which the routed event is defined.</param>
/// <param name="routedEvent">The routed event for which to remove the event handlers.</param>
public static void RemoveRoutedEventHandlers(UIElement element, RoutedEvent routedEvent)
{
    // Get the EventHandlersStore instance which holds event handlers for the specified element.
    // The EventHandlersStore class is declared as internal.
    var eventHandlersStoreProperty = typeof(UIElement).GetProperty(
        "EventHandlersStore", BindingFlags.Instance | BindingFlags.NonPublic);
    object eventHandlersStore = eventHandlersStoreProperty.GetValue(element, null);

    if (eventHandlersStore == null) return;

    // Invoke the GetRoutedEventHandlers method on the EventHandlersStore instance 
    // for getting an array of the subscribed event handlers.
    var getRoutedEventHandlers = eventHandlersStore.GetType().GetMethod(
        "GetRoutedEventHandlers", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
    var routedEventHandlers = (RoutedEventHandlerInfo[])getRoutedEventHandlers.Invoke(
        eventHandlersStore, new object[] { routedEvent });

    // Iteratively remove all routed event handlers from the element.
    foreach (var routedEventHandler in routedEventHandlers)
        element.RemoveHandler(routedEvent, routedEventHandler.Handler);
}

Answer 3

你不能，基本上 - 至少不是没有反思和很多贪婪。

事件严格“订阅，取消订阅” - 您不能取消订阅其他人的处理程序，只不过可以更改别人对某个对象的引用。

Answer 4

我在StackOverflow上找到了这个答案：

How to remove all event handlers from a control

private void RemoveClickEvent(Button b)
{
    FieldInfo f1 = typeof(Control).GetField("EventClick", 
        BindingFlags.Static | BindingFlags.NonPublic);
    object obj = f1.GetValue(b);
    PropertyInfo pi = b.GetType().GetProperty("Events",  
        BindingFlags.NonPublic | BindingFlags.Instance);
    EventHandlerList list = (EventHandlerList)pi.GetValue(b, null);
    list.RemoveHandler(obj, list[obj]);
}

原始海报发现here：

Answer 5

我的代码是Jamie Dixon发布的null错误问题，因为没有Click事件。

private void RemoveClickEvent(Control control)
{
    // chenged "FieldInfo f1 = typeof(Control)" to "var f1 = b.GetType()". By changing to 
    // the type of the  passed in control we can use this for any control with a click event.
    // using var allows for null checking and lowering the chance of exceptions.

    var fi = control.GetType().GetField("EventClick", BindingFlags.Static | BindingFlags.NonPublic);
    if (fi != null)
    {
        object obj = fi.GetValue(control);
        PropertyInfo pi = control.GetType().GetProperty("Events", BindingFlags.NonPublic | BindingFlags.Instance);
        EventHandlerList list = (EventHandlerList)pi.GetValue(control, null);
        list.RemoveHandler(obj, list[obj]);
    }

}

然后是一个小小的改变，应该适用于任何事件。

private void RemoveClickEvent(Control control, string theEvent)
{
    // chenged "FieldInfo f1 = typeof(Control)" to "var f1 = b.GetType()". By changing to 
    // the type of the  passed in control we can use this for any control with a click event.
    // using var allows for null checking and lowering the chance of exceptions.

    var fi = control.GetType().GetField(theEvent, BindingFlags.Static | BindingFlags.NonPublic);
    if (fi != null)
    {
        object obj = fi.GetValue(control);
        PropertyInfo pi = control.GetType().GetProperty("Events", BindingFlags.NonPublic | BindingFlags.Instance);
        EventHandlerList list = (EventHandlerList)pi.GetValue(control, null);
        list.RemoveHandler(obj, list[obj]);
    }

}

我想这可以做得更好，但它适合我目前的需要。希望这对某人有用。

Answer 6

我正在WinForms项目中工作，在该项目中，我必须从ToolStripMenuItem中删除click-EventHandler并将其替换为我自己的Handler。 （我必须修改单击contextMenu项时采取的操作）

对我来说，user2113340的代码不起作用。我必须像这样修改它才能与ToolStripMenuItem一起使用：

    private void RemoveClickEvent(ToolStripMenuItem control)
    {
        FieldInfo eventClick = typeof(Control).GetField("EventClick", BindingFlags.NonPublic | BindingFlags.Static);
        PropertyInfo eventsProp = typeof(Component).GetProperty("Events", BindingFlags.NonPublic | BindingFlags.Instance);
        EventHandlerList events = (EventHandlerList)eventsProp.GetValue(control, null);
        FieldInfo headInfo = events.GetType().GetField("head", BindingFlags.NonPublic | BindingFlags.Instance);
        object head = headInfo.GetValue(events);
        FieldInfo keyType = head.GetType().GetField("key", BindingFlags.NonPublic | BindingFlags.Instance);
        object key = keyType.GetValue(head);
        Delegate d1 = events[key];
        events.RemoveHandler(key, d1);
    }