static void OnChkPrimeDone( IAsyncResult iAr)
{
AsyncResult ar = iAr as AsynchResult;
CheckPrimeDelegate ckPrimDel = ar.AsyncDelegate as CheckPrimeDelegate;
bool isPrime = ckPrimDel.EndInvoke(ar);
Console.WriteLine(" Number is " + (isPrime? "prime ": "not prime");
}
