發生通用事件時調用方法

Question

我在嘗試實現對由應該在運行時定義的事件觸發的方法的調用時遇到問題。我發現這個答案：

Redirecting to a dynamic method from a generic event handler

並實現瞭解決方案，但我不斷收到異常時要調用的方法是一個實例之一，不是一成不變的。 這裏是我的部分代碼：

public class Operation 
{ 
    public bool EventFired 
    { 
     get { return _eventFired; } 
    } 

    private bool _eventFired = false; 

    public void Execute(object source, string EventName) 
    { 
     EventInfo eventInfo = source.GetType().GetEvent(EventName); 
     Delegate handler = null; 

     Type delegateHandler = eventInfo.EventHandlerType; 
     MethodInfo invokeMethod = delegateHandler.GetMethod("Invoke"); 
     ParameterInfo[] parms = invokeMethod.GetParameters(); 

     Type[] parmTypes = new Type[parms.Length]; 

     for (int i = 0; i < parms.Length; i++) 
      parmTypes[i] = parms[i].ParameterType; 

     DynamicMethod customMethod = new DynamicMethod 
      (
      "TempMethod", 
      invokeMethod.ReturnType, 
      parmTypes, 
      typeof (Operation).Module 
      ); 

     MethodInfo inf = typeof (Operation).GetMethod("SetFlag", BindingFlags.Instance | BindingFlags.Public); 

     ILGenerator ilgen = customMethod.GetILGenerator(); 
     ilgen.Emit(OpCodes.Ldarg_0); 
     ilgen.Emit(OpCodes.Call, inf); 
     ilgen.Emit(OpCodes.Ret); 

     //handler = _customMethod.CreateDelegate(delegateHandler);   // This works if I change SetFlag() to static 

     handler = customMethod.CreateDelegate(delegateHandler, this);  // I get an ArgumentException at this point: 
                      //Cannot bind to the target method because its signature 
                      //or security transparency is not compatible with that of the delegate type. 



     eventInfo.AddEventHandler(source, handler); 
    } 

    /// <summary>Signals that the event has been raised.</summary> 
    public void SetFlag() 
    { 
     _eventFired = true; 
    } 

} 

我不能找到一種方法來擺脫異常，代碼工作正常，如果我把SetFlag（）方法靜態的，但是這不是我所需要的。 任何建議將不勝感激。 在此先感謝。

Answer 1

我終於設法通過略微修改DynamicMethod的定義來解決問題，因爲在這個答案說明：

Reference 'this' in dynamic event handler

如果添加我的類類型的第一個值在類型陣列，其然後作爲參數傳遞給DynamicMethod，代理被正確創建並且它可以與實例方法一起使用！

public class Operation 
{ 
    public bool EventFired 
    { 
     get { return _eventFired; } 
    } 

    private bool _eventFired = false; 

    public void Execute(object source, string EventName) 
    { 
     EventInfo eventInfo = source.GetType().GetEvent(EventName); 
     Delegate handler = null; 

     Type delegateHandler = eventInfo.EventHandlerType; 
     MethodInfo invokeMethod = delegateHandler.GetMethod("Invoke"); 
     ParameterInfo[] parms = invokeMethod.GetParameters(); 

     Type[] parmTypes = new Type[parms.Length + 1]; 

     parmTypes[0] = this.GetType(); //First parameter is this class type. 

     for (int i = 0; i < parms.Length; i++) 
      parmTypes[i + 1] = parms[i].ParameterType; 

     DynamicMethod customMethod = new DynamicMethod 
            (
             "TempMethod", 
             invokeMethod.ReturnType, 
             parmTypes 
            ); 

     MethodInfo inf = typeof (Operation).GetMethod("SetFlag", BindingFlags.Instance | BindingFlags.Public); 

     ILGenerator ilgen = customMethod.GetILGenerator(); 
     ilgen.Emit(OpCodes.Ldarg_0); 
     ilgen.Emit(OpCodes.Call, inf); 
     ilgen.Emit(OpCodes.Ret); 

     handler = customMethod.CreateDelegate(delegateHandler, this);  

     eventInfo.AddEventHandler(source, handler); 
    } 

    /// <summary>Signals that the event has been raised.</summary> 
    public void SetFlag() 
    { 
     _eventFired = true; 
    } 

}