What does it mean to Call a Method Asynchronously? - in C#

To call a method and continue execution in the caller without waiting for the method to return. 


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using System;
using System.Threading;


namespace AsyncMethod
{
    class Program
    {
        // async method calls must be done through a delegate
        delegate double DoWorkDelegate(int maxValue);


        static void Main(string[] args)
        {
            DoWorkDelegate del = DoWork;


            //two ways to be notified of when method ends:
            // 1. callback method
            // 2. call EndInvoke
            IAsyncResult res =
                del.BeginInvoke(100000000, DoWorkDone, null);
            for (int i = 0; i < 5; i++)
            {
                Console.WriteLine("Doing other work...{0}", i);
                Thread.Sleep(1000);
            }


            //wait for end
            double sum = del.EndInvoke(res);
            Console.WriteLine("Sum: {0}", sum);
            Console.ReadKey();
        }


        static double DoWork(int maxValue)
        {
            Console.WriteLine("In DoWork");
            double sum = 0.0;
            for (int i = 1; i < maxValue; ++i)
            {
                sum += Math.Sqrt(i);
            }
            return sum;
        }


        static void DoWorkDone(object state)
        {
            //didn't pass in any state


            Console.WriteLine("Computation done");
        }
    }
}

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*Awesome definition: precise & concise


Source: C# 4.0 How-To - Real Solutions for C# 4.0 Programmers, by Ben Watson