blocks|key|1420078|text|目前，它们是按照注册的顺序执行的。然而，这是一个实现细节，我不会依赖于这个行为在未来的版本中保持不变，因为它不是规范所要求的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1420079|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Currently, they are executed in the order they are registered. However, this is an implementation detail, and I would not rely on this behavior staying the same in future versions, since it is not required by specifications.

blocks|key|1420100|text|您可以通过分离所有处理程序，然后按所需的顺序重新附加来更改顺序。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1420101|public+event+EventHandler+event1;

public+void+ChangeHandlersOrdering()
{
++++if+(event1+!=+null)
++++{
++++++++List<EventHandler>+invocationList+=+event1.GetInvocationList()
++++++++++++++++++++++++++++++++++++++++++++++++++.OfType<EventHandler>()
++++++++++++++++++++++++++++++++++++++++++++++++++.ToList();

++++++++foreach+(var+handler+in+invocationList)
++++++++{
++++++++++++event1+-=+handler;
++++++++}

++++++++//Change+ordering+now,+for+example+in+reverese+order+as+follows
++++++++for+(int+i+=+invocationList.Count+-+1;+i+>=+0;+i--)
++++++++{
++++++++++++event1+%2B=+invocationList[i];
++++++++}
++++}
}|code-block|syntax|javascript|1420102|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can change ordering by detaching all handlers, and then re-attaching in desired order.

<pre><code>public event EventHandler event1;

public void ChangeHandlersOrdering()
{
 if (event1 != null)
 {
 List&lt;EventHandler&gt; invocationList = event1.GetInvocationList()
 .OfType&lt;EventHandler&gt;()
 .ToList();

 foreach (var handler in invocationList)
 {
 event1 -= handler;
 }

 //Change ordering now, for example in reverese order as follows
 for (int i = invocationList.Count - 1; i &gt;= 0; i--)
 {
 event1 += invocationList[i];
 }
 }
}
</code></pre>

blocks|key|1204954|text|它们按照它们注册的顺序运行。RetrieveDataCompleted是一个Multicast+Delegates。我正在通过反射器来尝试和验证，它看起来像是在幕后使用了一个数组来跟踪所有事情。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1204955|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.multicastdelegate.aspx^0|E|L|12|J|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

They are run in the order in which they are registered. <code>RetrieveDataCompleted</code> is a <a href="http://msdn.microsoft.com/en-us/library/system.multicastdelegate.aspx" rel="noreferrer">Multicast Delegates</a>. I am looking through reflector to try and verify, and it looks like an array is used behind the scenes to keep track of everything.

blocks|key|1420111|text|如果有人需要在System.Windows.Forms.Form的上下文中执行此操作，这里有一个颠倒显示事件顺序的示例。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1420112|using+System;
using+System.ComponentModel;
using+System.Linq;
using+System.Reflection;
using+System.Windows.Forms;

namespace+ConsoleApplication+{
++++class+Program+{
++++++++static+void+Main()+{
++++++++++++Form+form;

++++++++++++form+=+createForm();
++++++++++++form.ShowDialog();

++++++++++++form+=+createForm();
++++++++++++invertShownOrder(form);
++++++++++++form.ShowDialog();
++++++++}

++++++++static+Form+createForm()+{
++++++++++++var+form+=+new+Form();
++++++++++++form.Shown+%2B=+(sender,+args)+=>+{+Console.WriteLine("form_Shown1");+};
++++++++++++form.Shown+%2B=+(sender,+args)+=>+{+Console.WriteLine("form_Shown2");+};
++++++++++++return+form;
++++++++}

++++++++static+void+invertShownOrder(Form+form)+{
++++++++++++var+events+=+typeof(Form)
++++++++++++++++.GetProperty("Events",+BindingFlags.Instance+%7C+BindingFlags.NonPublic)
++++++++++++++++.GetValue(form,+null)+as+EventHandlerList;

++++++++++++var+shownEventKey+=+typeof(Form)
++++++++++++++++.GetField("EVENT_SHOWN",+BindingFlags.NonPublic+%7C+BindingFlags.Static)
++++++++++++++++.GetValue(form);

++++++++++++var+shownEventHandler+=+events[shownEventKey]+as+EventHandler;

++++++++++++if+(shownEventHandler+!=+null)+{
++++++++++++++++var+invocationList+=+shownEventHandler
++++++++++++++++++++.GetInvocationList()
++++++++++++++++++++.OfType<EventHandler>()
++++++++++++++++++++.ToList();

++++++++++++++++foreach+(var+handler+in+invocationList)+{
++++++++++++++++++++events.RemoveHandler(shownEventKey,+handler);
++++++++++++++++}

++++++++++++++++for+(int+i+=+invocationList.Count+-+1;+i+>=+0;+i--)+{
++++++++++++++++++++events.AddHandler(shownEventKey,+invocationList[i]);
++++++++++++++++}
++++++++++++}
++++++++}
++++}
}|code-block|syntax|javascript|1420113|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If someone need to do this in the context of a System.Windows.Forms.Form, here is an example inverting the order of Shown event.

<pre><code>using System;
using System.ComponentModel;
using System.Linq;
using System.Reflection;
using System.Windows.Forms;

namespace ConsoleApplication {
 class Program {
 static void Main() {
 Form form;

 form = createForm();
 form.ShowDialog();

 form = createForm();
 invertShownOrder(form);
 form.ShowDialog();
 }

 static Form createForm() {
 var form = new Form();
 form.Shown += (sender, args) =&gt; { Console.WriteLine("form_Shown1"); };
 form.Shown += (sender, args) =&gt; { Console.WriteLine("form_Shown2"); };
 return form;
 }

 static void invertShownOrder(Form form) {
 var events = typeof(Form)
 .GetProperty("Events", BindingFlags.Instance | BindingFlags.NonPublic)
 .GetValue(form, null) as EventHandlerList;

 var shownEventKey = typeof(Form)
 .GetField("EVENT_SHOWN", BindingFlags.NonPublic | BindingFlags.Static)
 .GetValue(form);

 var shownEventHandler = events[shownEventKey] as EventHandler;

 if (shownEventHandler != null) {
 var invocationList = shownEventHandler
 .GetInvocationList()
 .OfType&lt;EventHandler&gt;()
 .ToList();

 foreach (var handler in invocationList) {
 events.RemoveHandler(shownEventKey, handler);
 }

 for (int i = invocationList.Count - 1; i &gt;= 0; i--) {
 events.AddHandler(shownEventKey, invocationList[i]);
 }
 }
 }
 }
}
</code></pre>

blocks|key|1205047|text|MulticastDelegate有一个链接的委托列表，称为调用列表，由一个或多个元素组成。当多播委托被调用时，调用列表中的委托将按照它们出现的顺序被同步调用。如果在列表执行过程中发生错误，则会抛出异常。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1205048|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

A MulticastDelegate has a linked list of delegates, called an invocation list, consisting of one or more elements. When a multicast delegate is invoked, the delegates in the invocation list are called synchronously in the order in which they appear. If an error occurs during execution of the list then an exception is thrown.

blocks|key|1205134|text|这是一个将新事件处理程序函数放在多委托调用列表中所需位置的函数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1205135|++++private+void+addDelegateAt(ref+YourDelegate+initial,+YourDelegate+newHandler,+int+position)
++++{
++++++++Delegate[]+subscribers+=+initial.GetInvocationList();
++++++++Delegate[]+newSubscriptions+=+new+Delegate[subscribers.Length+%2B+1];

++++++++for+(int+i+=+0;+i+<+newSubscriptions.Length;+i%2B%2B)
++++++++{
++++++++++++if+(i+<+position)
++++++++++++++++newSubscriptions[i]+=+subscribers[i];
++++++++++++else+if+(i==position)
++++++++++++++++newSubscriptions[i]+=+(YourDelegate)newHandler;
++++++++++++else+if+(i+>+position)
++++++++++++++++newSubscriptions[i]+=+subscribers[i-1];
++++++++}

++++++++initial+=+(YourDelegate)Delegate.Combine(newSubscriptions);
++++}|code-block|syntax|javascript|1205136|然后，你可以在代码中任何方便的地方删除带有'-=‘的函数。|1205137|PS+-我没有为'position‘参数做任何错误处理。|1205138|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

This is a function that will place the new event handler function wherever you want in the multidelegate invocation list.

<pre><code> private void addDelegateAt(ref YourDelegate initial, YourDelegate newHandler, int position)
 {
 Delegate[] subscribers = initial.GetInvocationList();
 Delegate[] newSubscriptions = new Delegate[subscribers.Length + 1];

 for (int i = 0; i &lt; newSubscriptions.Length; i++)
 {
 if (i &lt; position)
 newSubscriptions[i] = subscribers[i];
 else if (i==position)
 newSubscriptions[i] = (YourDelegate)newHandler;
 else if (i &gt; position)
 newSubscriptions[i] = subscribers[i-1];
 }

 initial = (YourDelegate)Delegate.Combine(newSubscriptions);
 }
</code></pre>

Then you can always remove the function with a '-=' wherever in your code convenient.

PS - I am not doing any error handling for the 'position' parameter.

blocks|key|1420159|text|我也遇到过类似的问题。在我的情况下，它很容易修复。我从未见过不使用%2B=运算符的委托。我的问题被修复了，因为总是在末尾添加一个委托，所有其他的总是在开头添加。OP的示例如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1420160|++++_webservice.RetrieveDataCompleted+=+_webservice.RetrieveDataCompleted+%2B+ProcessData1;
++++_webservice.RetrieveDataCompleted+=+ProcessData2+%2B+_webservice.RetrieveDataCompleted;|code-block|syntax|javascript|1420161|在第一种情况下，将最后调用ProcessData1。在第二种情况下，将首先调用ProcessData2。|1420162|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I had a similar problem. In my case it was fixed very easily. I'd never seen a delegate that didn't use the += operator. My problem was fixed by having one delegate always added at the end, all the others are always added at the beginning. The OP's example would be something like:

<pre><code> _webservice.RetrieveDataCompleted = _webservice.RetrieveDataCompleted + ProcessData1;
 _webservice.RetrieveDataCompleted = ProcessData2 + _webservice.RetrieveDataCompleted;
</code></pre>

In the first case ProcessData1 will be called last. In the 2nd case ProcessData2 will be called first.

blocks|key|1420224|text|一个简约的例子来说明顺序可以不同于它被添加的顺序。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1420225|public+class+TestClass
{
++++Delegate+handlers;

++++public+event+EventHandler+Event
++++{
++++++++add+{+handlers+=+Delegate.Combine(value,+handlers+);+}+//+<--+note+the+order
++++++++remove+{+handlers+=+Delegate.Remove(handlers,+value);+}
++++}

++++public+void+RaiseEvents()
++++{
++++++++handlers?.DynamicInvoke(this,+EventArgs.Empty);
++++}
}|code-block|syntax|javascript|1420226|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

A minimalistic example to show that the order can differ from the order it was added.
<pre><code>public class TestClass
{
 Delegate handlers;

 public event EventHandler Event
 {
 add { handlers = Delegate.Combine(value, handlers ); } // &lt;-- note the order
 remove { handlers = Delegate.Remove(handlers, value); }
 }

 public void RaiseEvents()
 {
 handlers?.DynamicInvoke(this, EventArgs.Empty);
 }
}
</code></pre>

If I set up multiple event handlers, like so:

<pre><code>_webservice.RetrieveDataCompleted += ProcessData1;
_webservice.RetrieveDataCompleted += ProcessData2;
</code></pre>

what order are the handlers run when the event <code>RetrieveDataCompleted</code> is fired? Are they run in the same thread and sequentially in the order that are registered?

Order of event handler execution

Windows

如果我设置了多个事件处理程序，如下所示：_webservice.RetrieveDataCompleted += ProcessData1;_webservice.RetrieveDataCompleted += ProcessData2;触发事件RetrieveDataCompleted时，处理程序的运行顺序是什么？它们是否在同一个线程中运行，并且按照注册的顺序顺序运行？

问事件处理程序的执行顺序
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