Write factorial using ADI

AsyncAwait_WriteFactorialAsyncUsingDelegate

private void WriteFactorialAsyncUsingDelegate(int facno)
{
    Func<int, int> findFact = FindFactorialWithSimulatedDelay;
    findFact.BeginInvoke(facno, 
                        (iAsyncresult) =>
                                {
                                    AsyncResult asyncResult = iAsyncresult as AsyncResult;
                                    Func<int, int> del = asyncResult.AsyncDelegate as Func<int, int>;
                                    int factorial = del.EndInvoke(asyncResult);
                                    Console.WriteLine("Factorial of {0} is {1}", facno, factorial);
                                }, 
                        null);
}