要在控件上创建新的事件处理程序,可以这样做
c.Click += new EventHandler(mainFormButton_Click);
或者这个
c.Click += mainFormButton_Click;
要删除事件处理程序,可以这样做
c.Click -= mainFormButton_Click;
但是如何从事件中删除所有事件处理程序呢?
要在控件上创建新的事件处理程序,可以这样做
c.Click += new EventHandler(mainFormButton_Click);
或者这个
c.Click += mainFormButton_Click;
要删除事件处理程序,可以这样做
c.Click -= mainFormButton_Click;
但是如何从事件中删除所有事件处理程序呢?
当前回答
实际上我在用这个方法,效果很好。我受到了Aeonhack写的代码的“启发”。
Public Event MyEvent()
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
If MyEventEvent IsNot Nothing Then
For Each d In MyEventEvent.GetInvocationList ' If this throws an exception, try using .ToArray
RemoveHandler MyEvent, d
Next
End If
End Sub
~MyClass()
{
if (MyEventEvent != null)
{
foreach (var d in MyEventEvent.GetInvocationList())
{
MyEventEvent -= (MyEvent)d;
}
}
}
字段MyEventEvent是隐藏的,但它确实存在。
调试过程中,你可以看到d.t target是如何实际处理事件的对象,而d.m ode是如何处理事件的方法。你只需要把它拿掉。
效果很好。不再有对象因为事件处理程序而被GC。
其他回答
我讨厌这里展示的任何完整的解决方案,我现在做了一个混合和测试,为任何事件处理程序工作:
public class MyMain()
public void MyMethod() {
AnotherClass.TheEventHandler += DoSomeThing;
}
private void DoSomething(object sender, EventArgs e) {
Debug.WriteLine("I did something");
AnotherClass.ClearAllDelegatesOfTheEventHandler();
}
}
public static class AnotherClass {
public static event EventHandler TheEventHandler;
public static void ClearAllDelegatesOfTheEventHandler() {
foreach (Delegate d in TheEventHandler.GetInvocationList())
{
TheEventHandler -= (EventHandler)d;
}
}
}
简单!感谢Stephen Punak。
我使用它是因为我使用一个通用的本地方法来删除委托,当设置不同的委托时,在不同的情况下调用本地方法。
虽然有点晚了,但我使用了这个对我来说非常有效的链接: https://www.codeproject.com/Articles/103542/Removing-Event-Handlers-using-Reflection
这个代码的美妙之处在于它适用于所有人,WFP, Forms, Xamarin Forms。我用它来做沙玛林。请注意,只有当你不拥有这个事件(例如,一个库代码在你不关心的一些事件上崩溃)时,你才需要这种方式使用Reflection。
下面是我稍微修改过的代码:
static Dictionary<Type, List<FieldInfo>> dicEventFieldInfos = new Dictionary<Type, List<FieldInfo>>();
static BindingFlags AllBindings
{
get { return BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static; }
}
static void BuildEventFields(Type t, List<FieldInfo> lst)
{
foreach (EventInfo ei in t.GetEvents(AllBindings))
{
Type dt = ei.DeclaringType;
FieldInfo fi = dt.GetField(ei.Name, AllBindings);
if (fi != null)
lst.Add(fi);
}
}
static List<FieldInfo> GetTypeEventFields(Type t)
{
if (dicEventFieldInfos.ContainsKey(t))
return dicEventFieldInfos[t];
List<FieldInfo> lst = new List<FieldInfo>();
BuildEventFields(t, lst);
dicEventFieldInfos.Add(t, lst);
return lst;
}
static EventHandlerList GetStaticEventHandlerList(Type t, object obj)
{
MethodInfo mi = t.GetMethod("get_Events", AllBindings);
return (EventHandlerList)mi.Invoke(obj, new object[] { });
}
public static void RemoveEventHandler(object obj, string EventName = "")
{
if (obj == null)
return;
Type t = obj.GetType();
List<FieldInfo> event_fields = GetTypeEventFields(t);
EventHandlerList static_event_handlers = null;
foreach (FieldInfo fi in event_fields)
{
if (EventName != "" && string.Compare(EventName, fi.Name, true) != 0)
continue;
var eventName = fi.Name;
// After hours and hours of research and trial and error, it turns out that
// STATIC Events have to be treated differently from INSTANCE Events...
if (fi.IsStatic)
{
// STATIC EVENT
if (static_event_handlers == null)
static_event_handlers = GetStaticEventHandlerList(t, obj);
object idx = fi.GetValue(obj);
Delegate eh = static_event_handlers[idx];
if (eh == null)
continue;
Delegate[] dels = eh.GetInvocationList();
if (dels == null)
continue;
EventInfo ei = t.GetEvent(eventName, AllBindings);
foreach (Delegate del in dels)
ei.RemoveEventHandler(obj, del);
}
else
{
// INSTANCE EVENT
EventInfo ei = t.GetEvent(eventName, AllBindings);
if (ei != null)
{
object val = fi.GetValue(obj);
Delegate mdel = (val as Delegate);
if (mdel != null)
{
foreach (Delegate del in mdel.GetInvocationList())
{
ei.RemoveEventHandler(obj, del);
}
}
}
}
}
}
示例用法:RemoveEventHandler(obj, "Focused");
从删除所有事件处理程序:
Directly no, in large part because you cannot simply set the event to null. Indirectly, you could make the actual event private and create a property around it that tracks all of the delegates being added/subtracted to it. Take the following: List<EventHandler> delegates = new List<EventHandler>(); private event EventHandler MyRealEvent; public event EventHandler MyEvent { add { MyRealEvent += value; delegates.Add(value); } remove { MyRealEvent -= value; delegates.Remove(value); } } public void RemoveAllEvents() { foreach(EventHandler eh in delegates) { MyRealEvent -= eh; } delegates.Clear(); }
我在MSDN论坛上找到了一个解决方案。下面的示例代码将删除button1中的所有Click事件。
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
button1.Click += button1_Click;
button1.Click += button1_Click2;
button2.Click += button2_Click;
}
private void button1_Click(object sender, EventArgs e) => MessageBox.Show("Hello");
private void button1_Click2(object sender, EventArgs e) => MessageBox.Show("World");
private void button2_Click(object sender, EventArgs e) => RemoveClickEvent(button1);
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]);
}
}
这不是对OP的回答,但我想我把它贴在这里,以防它能帮助到其他人。
/// <summary>
/// Method to remove a (single) SocketAsyncEventArgs.Completed event handler. This is
/// partially based on information found here: http://stackoverflow.com/a/91853/253938
///
/// But note that this may not be a good idea, being very .Net implementation-dependent. Note
/// in particular use of "m_Completed" instead of "Completed".
/// </summary>
private static void RemoveCompletedEventHandler(SocketAsyncEventArgs eventArgs)
{
FieldInfo fieldInfo = typeof(SocketAsyncEventArgs).GetField("m_Completed",
BindingFlags.Instance | BindingFlags.NonPublic);
eventArgs.Completed -= (EventHandler<SocketAsyncEventArgs>)fieldInfo.GetValue(eventArgs);
}