AsyncTask

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Remoting.Messaging;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApp25
{
    class Program
    {
        delegate string MyDelegate(int a, out int b);
        static void Main(string[] args)
        {
            WithPolling();
        }

        public static void MyCallback(IAsyncResult ar)
        {
            //int b = 0;
            //string str = ((AsyncResult)ar).AsyncDelegate.EndInvoke(out b, ar);
            //Console.WriteLine(str + ": the b returned is: " + b);
        }

        public static void WithPolling()
        {
            MyDelegate dlg = new MyDelegate(MyMethod);
            int b = 0;
            IAsyncResult ar = dlg.BeginInvoke(2000, out b, null, null);
            Console.WriteLine("Some additional work - {0}", b);
            int count = 0;
            while(!ar.IsCompleted)
            {
                count++;
                Thread.Sleep(100);
                //Console.WriteLine("Continue doing other work");
                //continue doing other work
            }
            Console.WriteLine("Counter: {0}", count);

            //end work
            ar.AsyncWaitHandle.WaitOne(9000);
            String str = dlg.EndInvoke(out b, ar);
            Console.WriteLine(str + ": the b returned is: " + b);
            Console.ReadKey();
        }

        public static void WithWaitable()
        {
            MyDelegate dlg = new MyDelegate(MyMethod);
            int b = 0;
            IAsyncResult ar = dlg.BeginInvoke(1000, out b, null, null);
            Console.WriteLine("Some additional work - {0}", b);
            //end work
            ar.AsyncWaitHandle.WaitOne(9000);
            Console.WriteLine("End of waitone()");
            String str = dlg.EndInvoke(out b, ar);
            Console.WriteLine(str + ": the b returned is: " + b);
            Console.ReadKey();
        }

        public static void WithEndInvoke()
        {
            MyDelegate dlg = new MyDelegate(MyMethod);
            int b = 0;
            IAsyncResult ar = dlg.BeginInvoke(3000, out b, null, null);
            Console.WriteLine("Some additional work - {0}", b);
            //end work
            String str = dlg.EndInvoke(out b, ar);
            Console.WriteLine(str + ": the b returned is: " + b);
            Console.ReadKey();
        }

        public static string MyMethod(int a, out int b)
        {
            Thread.Sleep(a);
            b = Thread.CurrentThread.GetHashCode();
            return "Returned from my asynchronous method";
        }
    }
}