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        如何使用反射将事件处理程序附加到事件?

        How to attach event handler to an event using reflection?(如何使用反射将事件处理程序附加到事件?)
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                2. 本文介绍了如何使用反射将事件处理程序附加到事件?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着跟版网的小编来一起学习吧!

                  问题描述

                  我知道 EventInfo.AddEventHandler(...) 方法,该方法可用于将处理程序附加到事件.但是,如果我什至无法定义事件处理程序的正确签名,例如,我什至没有对处理程序预期的事件参数的引用,该怎么办?

                  I know about EventInfo.AddEventHandler(...) method which can be used to attach handler to an event. But what should be done if i can not even define proper signature of the event handler, as in, i don't even have reference to the event args expected by the handler?

                  我会用正确的代码解释问题.

                  I will explain the problem with the proper code.

                  //解决方案中所有可用的场景,零反射场景.

                  // Scenario when I have everything available in my solution, Zero Reflection Scenario.

                  internal class SendCommentsManager
                  {
                      public void Customize(IRFQWindowManager rfqWindowManager)
                      {
                          rfqWindowManager.SendComment += HandleRfqSendComment;
                      }
                  
                      private void HandleRfqSendComment(object sender, SendCommentEventArgs args)
                      {
                          args.Cancel = true;
                      }
                  }
                  

                  现在,我想通过使用反射来实现相同的目标.我已经能够弄清楚其中的大部分,但是当我将委托附加到事件时(使用 AddEventHandler)它会抛出 "Error binding to target method." 异常.

                  Now, I want to achieve the same objective by using reflection. I have been able to figure out most of it but when i attach a delegate to the event (using AddEventHandler) it throws "Error binding to target method." exception.

                  我了解此异常背后的原因,将错误的委托附加到事件.但必须有某种方法来实现这一点.

                  I understand the reason behind this exception, attaching a wrong delegate to an event. But there must be some way to achieve this.

                   internal class SendCommentsManagerUsingReflection
                   {
                       public void Customize(IRFQWindowManager rfqWindowManager)
                       {
                           EventInfo eventInfo = rfqWindowManager.GetType().GetEvent("SendComment");
                           eventInfo.AddEventHandler(rfqWindowManager, 
                               Delegate.CreateDelegate(eventInfo.EventHandlerType, this, "HandleRfqSendComment"));
                           //<<<<<<<<<<ABOVE LINE IS WHERE I AM GOING WRONG>>>>>>>>>>>>>>
                       }
                  
                       private void HandleRfqSendComment(object sender, object args)
                       {
                           Type sendCommentArgsType = args.GetType();
                           PropertyInfo cancelProperty = sendCommentArgsType.GetProperty("Cancel");
                           cancelProperty.SetValue(args, true, null);
                       }
                   }
                  

                  推荐答案

                  我认为您的代码失败了,因为 HandleRfqSendComment 是私有的.相反,您可以直接为该方法创建一个委托,而无需将其名称传递给 CreateDelegate.然后,您需要使用以下方法将委托转换为所需的类型:

                  I think your code is failing because the HandleRfqSendComment is private. Instead you could directly create a delegate to that method, without passing its name to CreateDelegate. You would then need to convert the delegate to the required type, using the following method :

                  public static Delegate ConvertDelegate(Delegate originalDelegate, Type targetDelegateType)
                  {
                      return Delegate.CreateDelegate(
                          targetDelegateType,
                          originalDelegate.Target,
                          originalDelegate.Method);
                  }
                  

                  在您的代码中,您可以按如下方式使用此方法:

                  In your code, you could use this method as follows :

                  EventInfo eventInfo = rfqWindowManager.GetType().GetEvent("SendComment");
                  Action<object, object> handler = HandleRfqSendComment;
                  Delegate convertedHandler = ConvertDelegate(handler, eventInfo.EventHandlerType);
                  eventInfo.AddEventHandler(rfqWindowManager, convertedHandler);
                  

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