Speeding up Reflection Invoke C#/.NET

Question

There are plenty of posts on speeding up reflection invokes, examples here:

Speeding up Reflection API with delegate in .NET/C#

https://codeblog.jonskeet.uk/2008/08/09/making-reflection-fly-and-exploring-delegates/

and here:

Example : Speeding up Reflection API with delegate in .NET/C#

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My question is about speeding up generic invokes. Is this possible at all?

I've got an abstract class and a class which implements it...

public abstract class EncasulatedMessageHandler<T> where T : Message
{
    public abstract void HandleMessage(T message);
}

public class Handler : EncasulatedMessageHandler<MyMessageType>
{
    public int blat = 0;
    public override void HandleMessage(MyMessageType message) { blat++; }
}

What I want to do is build up a list of these message handler classes and quickly invoke their HandleMessage()

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At the moment, I'm doing something that's approximately this:

object handler = Activator.CreateInstance(typeof(Handler)); // Ignore this, this is done up front.

MethodInfo method = type.GetMethod("HandleMessage", BindingFlags.Instance | BindingFlags.Public);

Action<object> hook = new Action<object>(delegate(object message)
{
    method.Invoke(handler, new object[] { message });
});

// Then when I want to invoke it:

hook(new MyMessageType());

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That's not the whole thing, but it's the important stuff...

The method.Invoke is very slow, I'd like to keep the generic parameters on the class, I realise I could lock this down to object and cast it in the HandleMessage method, but I'm trying to avoid doing this.

Is there anything I can do to speed this up? It's currently orders of magnitude slower than direct calls.

Any help would be appreciated.

Answer 1

Using Delegate.CreateDelegate() should be a lot faster. You will end up with a pointer to the real function, not a delegate that calls Invoke().

Try this:

object handler = Activator.CreateInstance(typeof(Handler)); 
var handlerType = handler.GetType();
var method = handlerType.GetMethod("HandleMessage", BindingFlags.Instance | BindingFlags.Public);
var paramType = handlerType.GetGenericArguments()[0];

// invoke the MakeHandleMessageDelegate method dynamically with paramType as the type parameter
// NB we're only doing this once
Action<object> hook = (Action<object>) this.GetType().GetMethod("MakeHandleMessageDelegate")
            .MakeGenericMethod(paramType)
            .Invoke(null, new [] { handler });

In the same class add the following generic method. We invoke this dynamically above because we don't know the type parameter at compile time.

public static Action<object> MakeHandleMessageDelegate<T>(object target)
{
    var d = (Action<T>)Delegate.CreateDelegate(typeof(Action<T>), target, "HandleMessage");

    // wrap the delegate another that simply casts the object parameter to the required type
    return param => d((T)param);
}

You then have a delegate that casts the parameter to the required type, then calls the HandleMessage method.