Generating Delegate Types dynamically in C#

Question

We have a requirement where we need to generate delegate types on the fly. We need to generate delegates given the input parameters and the output. Both input and output wou

Answer 1

Jon's answer works fine if you're running framework 3.5 (but not everyone is).

The 2.0 answer is to use Delegate.CreateDelegate(...)

http://msdn.microsoft.com/en-us/library/system.delegate.createdelegate.aspx

A comparison of various ways to do this including Jon's Func, Delegate.CreateDelegate, DynamicMethods and various other tricks was discussed on an earlier thread:

Delegate.CreateDelegate vs DynamicMethod vs Expression

-Oisin

Answer 2

The simplest way would be to use the existing Func family of delegates.

Use typeof(Func<,,,,>).MakeGenericType(...). For example, for your int Del2(int, int, string, int) type:

using System;

class Test
{
    static void Main()
    {
        Type func = typeof(Func<,,,,>);
        Type generic = func.MakeGenericType
            (typeof(int), typeof(int), typeof(string),
             typeof(int), typeof(int));
        Console.WriteLine(generic);
    }
}

If you really, really need to create a genuinely new type, perhaps you could give some more context to help us help you better.

EDIT: As Olsin says, the Func types are part of .NET 3.5 - but if you want to use them in .NET 2.0, you just have to declare them yourself, like this:

public delegate TResult Func<TResult>();
public delegate TResult Func<T, TResult>(T arg);
public delegate TResult Func<T1, T2, TResult>(T1 arg1, T2 arg2);
public delegate TResult Func<T1, T2, T3, TResult>
    (T1 arg1, T2 arg2, T3 arg3);
public delegate TResult Func<T1, T2, T3, T4, TResult>
    (T1 arg1, T2 arg2, T3 arg3, T4 arg4);

If 4 arguments isn't enough for you, you can add more of course.