CODEWITHSUNDEEP
c#reflectiondelegates
IAbstract
IAbstract

Reputation: 19881

Building delegate handler collection

I have an implementation building a delegate handler collection.

   public class DelegateHandler
   {
            internal delegate object delegateMethod(object args);
            public IntPtr PublishAsyncMethod(MethodInfo method, MethodInfo callback)
            {
                RuntimeMethodHandle rt;

                try
                {
                    rt = method.MethodHandle;
                    delegateMethod dMethod = (delegateMethod)Delegate.CreateDelegate
                        (typeof(delegateMethod), method.ReflectedType, method, true);
                    AsyncCallback callBack = (AsyncCallback)Delegate.CreateDelegate
                        (typeof(AsyncCallback), method.ReflectedType, callback, true);

                    handlers[rt.Value] = new DelegateStruct(dMethod, callBack);
                    return rt.Value;
                }
                catch (System.ArgumentException ArgEx)
                {
                    Console.WriteLine("*****: " + ArgEx.Source);
                    Console.WriteLine("*****: " + ArgEx.InnerException);
                    Console.WriteLine("*****: " + ArgEx.Message);
                }

                return new IntPtr(-1);
            }
   }

I publish using the following:

 ptr = DelegateHandler.Io.PublishAsyncMethod(
    this.GetType().GetMethod("InitializeComponents"),
    this.GetType().GetMethod("Components_Initialized"));

And the method I'm creating a delegate from:

    public void InitializeComponents(object args)
    { 
           // do stuff;
    }

And the callback method:

public void Components_Initialized(IAsyncResult iaRes)
{
       // do stuff;
}

Now, I've also already looked at this to get an idea of what I might be doing wrong. The CreateDelegate(...) is causing me to receive:

*****: mscorlib
*****: 
*****: Error binding to target method.

What is wrong? The methods reside in a different, non-static public class. Any help would be greatly appreciated.

NOTE: These methods will have parameters and return values. As I understand Action, and Action<T>, this would not be an option.

Upvotes: 1

Views: 909

Answers (1)

Nick Guerrera
Nick Guerrera

Reputation: 2549

There are 2 problems.

First, you are passing incorrect arguments to CreateDelegate. Since you are binding to instance methods, you need to pass the instance to which the delegates will be bound, but you are passing method.ReflectedType instead of a reference to an object of the class that declares InitializeComponents and Components_Initialized.

Second, the signature of InitializeComponents does not match the declaration of delegate dMethod. The delegate has an object return type yet InitializeComponents returns void.

The following should work:

// return type changed to void to match target.
internal delegate void delegateMethod(object args);

// obj parameter added
public static void PublishAsyncMethod(object obj, MethodInfo method, MethodInfo callback)
{
    delegateMethod dMethod = (delegateMethod)Delegate.CreateDelegate
        (typeof(delegateMethod), obj, method, true);

    AsyncCallback callBack = (AsyncCallback)Delegate.CreateDelegate
         (typeof(AsyncCallback), obj, callback);

}

DelegateHandler.PublishAsyncMethod(
    this, // pass this pointer needed to bind instance methods to delegates.
    this.GetType().GetMethod("InitializeComponents"),
    this.GetType().GetMethod("Components_Initialized"));

Upvotes: 1

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