APM和计算限制的操作--CLR via c#

计算1到n的数字之和:

static void Main(string[] args)
        {
            Func<UInt64, UInt64> sumDelegate = Sum;

            sumDelegate.BeginInvoke(1000000000,SumIsDone,sumDelegate);

            Console.WriteLine("Calculating....");
            Console.ReadLine();
        }

        private static UInt64 Sum(UInt64 n)
        {
            UInt64 sum = 0;

            for (UInt64 i = 0; i < n; i++)
            {
                checked {
                    sum += i;
                }                
            }

            return sum;               
        }

        private static void SumIsDone(IAsyncResult iar)
        {
            var sumDelegate = (Func<UInt64, UInt64>)iar.AsyncState;

            try
            {
                Console.WriteLine("Sum's result: "+sumDelegate.EndInvoke(iar));
            }
            catch (OverflowException)
            {
                Console.WriteLine("Sum's result is too large to calculate");
            }
        }