我有一个按钮控件，我需要删除所有附加到其Click event 的事件处理程序。
这怎么可能？
Button button = GetButton();
button.Click.RemoveAllEventHandlers();
【问题讨论】：
标签： c# .net events event-handling
我正在处理 WinForms 项目，我必须从 ToolStripMenuItem 中删除 click-EventHandler 并将其替换为我自己的处理程序。 （我必须修改单击 contextMenu 项时采取的操作）
对我来说，来自 user2113340 的代码不起作用。我不得不像这样修改它以使用 ToolStripMenuItem：
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);
}
【讨论】：
注意：由于我发布原始答案的问题已关闭as a duplicate 这个问题，我在这里交叉发布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，您可以轻松地将其转换为扩展方法。
/// <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);
编辑：我复制了bug fix implemented by corona，它会在没有订阅事件处理程序时阻止该方法抛出NullReferenceException。信用（和赞成）应该去他们的答案。
【讨论】：
只是想稍微扩展一下道格拉斯的常规，我非常喜欢。 我发现我需要向 eventHandlersStore 添加额外的 null 检查以处理传递的元素尚未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);
}
【讨论】：
Jamie Dixon 发布的代码出现空错误问题，考虑到没有 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]);
}
}
然后是一个小的变化，它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，但它可以满足我当前的需求。希望这对某人有用。
【讨论】：
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]);
}
原始发帖人找到了here：
【讨论】：
你不能，基本上 - 至少不能没有反思和很多肮脏。
事件严格来说是“订阅、取消订阅”——您不能取消订阅其他人的处理程序，就像您不能更改其他人对对象的引用一样。
【讨论】：