//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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