How do you examine the arguments passed to a delegate?

Question

I'm trying to make a class to handle invoking methods on a remote server using my own means. To make it easier on the client caller, I'm writing a generic class that accepts an interface so that the compiler will know the number of arguments and the return type of the method.

public class Service<TInterface>
{
    public TResult Invoke<TResult>(Func<TInterface, TResult> function)
    {
        // Do the work
    }
}

So the idea is they could reference an assembly that has the interfaces, for example:

public interface ICalculator
{
    int Add(int num1, int num2);
}

And then they could write code to hit the service like this:

var addend = new Service<ICalculator>(/* constructor */).Invoke(s => s.Add(3, 4));

The problem is that in the first code block, I need to know how to find out what arguments they passed in their lamda expression. How do I do that?

Answer 1

The easiest way to do that is to take an Expression<Func<TInterface,TResult> instead; this is then trivial to pull apart. In fact, you can just lift my code from here which covers most scenarios. In particular, look at ResolveMethod. Some discussion/explanation for this is here.