using System;

using System.Threading;

​

public class Program

{

    //1. Way

    delegate TResult MethodCaller<T1, T2, TResult>(T1 arg1, T2 arg2);

    //2. Way

    //delegate TResult MethodCaller<T1, T2, TResult>(T1 arg1, T2 arg2);

    public static void Main(string[] args)

    {

        MethodCaller<int, int, int> funcDelegate = DoWork;

        IAsyncResult asyncResult = funcDelegate.BeginInvoke(30, 20, null, null);

        Console.WriteLine($"Main thread {Thread.CurrentThread.ManagedThreadId} does some work.");

        Thread.Sleep(TimeSpan.FromSeconds(2));

        int result = funcDelegate.EndInvoke(asyncResult);

        Console.WriteLine($"DoWork(30, 20) returned {result}");

    }

​

    static int DoWork(int num1, int num2)

    {

        Console.WriteLine($"Test method begins in thread {Thread.CurrentThread.ManagedThreadId}");

        Thread.Sleep(TimeSpan.FromSeconds(3));

        return num1 + num2;

    }

}