C# 的异步调用

使用异步调用，某些时候可以提高性能，比如说写日志，对数据库进行操作的时候就可以使用异步操作的方式。这种方式相当于多线程并发运行，所以性能会有所提升。我后面会发篇随笔来使用异步调用的方法写日志。

/*
 * Authod: sandals
 * Date  : 2010-08-07 20:30
 * Description: 异步调用的实现
 * */

using System;
namespace Sandals.Demo.AsynchronousCall
{
    public static class AsyncDemo
    {
　　　　 //声明委托
        private delegate string AsyncMethodCalledEventHander(int duration, out int threadId);
       //create an instance of the delegate
        private static AsyncMethodCalledEventHander eventHandler = new AsyncMethodCalledEventHander(MethodForAsyncCall);

        /// <summary>
        /// The method to be executed asynchronously
        /// </summary>
        /// <param name="duration">sleep duration for thread</param>
        /// <param name="threadId">current thread id</param>
        /// <returns></returns>
        private static string MethodForAsyncCall(int duration, out int threadId)
        {
            Console.WriteLine("MethodForAsyncCall begin execute... ");
            System.Threading.Thread.Sleep(duration);
            threadId = System.Threading.Thread.CurrentThread.ManagedThreadId;
            return String.Format("my execute time was {0} ", duration);
        }

        /// <summary>
        /// this method for executing asyc method
        /// </summary>
        /// <param name="duration"></param>
        /// <returns></returns>
        public static IAsyncResult BeingRun(int duration)
        {
            int dumy;
            IAsyncResult result = eventHandler.BeginInvoke(duration, out dumy, null, null);
            return result;
        }

        /// <summary>
        /// this methiod end the asyc method
        /// </summary>
        /// <param name="threadId"></param>
        /// <param name="ar"></param>
        /// <returns></returns>
        public static string EndRun(out int threadId, IAsyncResult ar)
        {
            if (ar == null)
                throw new NullReferenceException("parameter ar can not be a null");
            return eventHandler.EndInvoke(out threadId, ar);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            IAsyncResult result = AsyncDemo.BeingRun(10000);
            Console.WriteLine("the thread {0} continue to execute", System.Threading.Thread.CurrentThread.ManagedThreadId);

            Console.WriteLine("the thread {0} begin to sleep, date: {1}", System.Threading.Thread.CurrentThread.ManagedThreadId, DateTime.Now);
            System.Threading.Thread.Sleep(3000);
            Console.WriteLine("the thread {0} sleep end, date: {1}", System.Threading.Thread.CurrentThread.ManagedThreadId, DateTime.Now);

            int threadId = 0;
            Console.WriteLine("call the mothod to end the ansychronous method");
            Console.WriteLine("asynchronous method return value: {0}. thread id: {1}", AsyncDemo.EndRun(out threadId, result), threadId);
        }
    }
}