Async Delegates Callback

   
 

using System;
using System.Threading;
   
class AsyncDelegatesCallback
{
    public static int Add(int op1, int op2, out int result)
    {
        Thread.Sleep(1000); 
        return (result = op1 + op2);
    }
    public delegate int AddDelegate(int op1, int op2,
        out int result);
   
    public static void AnnounceSum(IAsyncResult iar)
    {
        AddDelegate add = (AddDelegate)iar.AsyncState;
   
        int result;
        add.EndInvoke(out result, iar);
   
        Console.WriteLine("[AnnounceSum] The result is {0}", result);
    }
   
    static void Main()
    {
        int result;
        AddDelegate add = new AddDelegate(Add);
        add.BeginInvoke(6, 42, out result, new AsyncCallback(AnnounceSum), add);
   
        Thread.Sleep(1000); 
    }
}