//异步io的一个例子， 不明白？？？？ 异步为什么那样复杂，以及异步io的步骤。using System;using System.Collections.Generic;using System.Text;using System.IO;using System.Threading; namespace _5_10{    public class filereader    {        const string path = "E:\\1.txt";         public void synccall()        //同步的        {            FileStream fs = new FileStream(path,FileMode.Open,FileAccess.Read,FileShare.Read,1024,false);            int x = 0;            while ((x = fs.ReadByte())!= -1) { }            fs.Close();            Console.WriteLine("synchro open finished "+DateTime.Now);        }         public void asynccall()    //异步的        {            FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, 1024, true);            worddocstate state = new worddocstate();            state.fs = fs;            state.content = new byte[fs.Length];            state.resetevent = new AutoResetEvent(false);            AsyncCallback readdoccallback = new AsyncCallback(ReadDocCallback);            fs.BeginRead(state.content,0,(int)state.fs.Length,ReadDocCallback,state);            state.resetevent.WaitOne();            Console.WriteLine("async open finished "+DateTime.Now);         }         private void ReadDocCallback(IAsyncResult asyncresult)        {            worddocstate state = (worddocstate)asyncresult.AsyncState;            FileStream stream = state.fs;            int bytesread = stream.EndRead(asyncresult);            stream.Close();            state.resetevent.Set();        }         public class worddocstate        {            public FileStream fs;            public byte[] content;            public AutoResetEvent resetevent;        }           static void Main(string[] args)        {            filereader fr = new filereader();                       fr.synccall();            fr.asynccall();        }    }}

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