C#实现异步读取文件

异步读取文件，读取完成之后触发事件，通知主线程。主线程与读取文件的线程互相独立。

代码

using System;

using System.Collections.Generic;

using System.Text;

using System.IO;

using System.Diagnostics;

using System.Threading;

namespace ExToDB.FileTransfer

{

///

public class AsyncProcessor

{

private Stream inputStream;

public Stream InputStream

{

get { return inputStream; }

set { inputStream = value; }

}

// 每次读取块的大小

private int bufferSize = 2048;

public event ReturnEndEvent IsReturnEvent;

protected void OnIsReturnEvent()

{

if (IsReturnEvent != null)

IsReturnEvent(this, new ReturnEndReadEventargs(true));

}

public int BufferSize

{

get { return bufferSize; }

set { bufferSize = value; }

}

// 容纳接收数据的缓存

private byte[] buffer;

public AsyncProcessor(string fileName)

{

buffer = new byte[bufferSize];

// 打开文件，指定参数为true以提供对异步操作的支持

inputStream = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize, true);

}

///

public void StartProcess()

{

// 开始异步读取文件，填充缓存区

inputStream.BeginRead(buffer, 0, buffer.Length, OnCompletedRead, null);

}

private void OnCompletedRead(IAsyncResult asyncResult)

{

// 已经异步读取一个 块 ，接收数据

int bytesRead = inputStream.EndRead(asyncResult);

// 如果没有读取任何字节，则流已达文件结尾

if (bytesRead > 0)

{

// 暂停以模拟对数据块的处理

Debug.WriteLine(\" 异步线程：已读取一块\");

Thread.Sleep(TimeSpan.FromMilliseconds(20));

// 开始读取下一块

inputStream.BeginRead(buffer, 0, buffer.Length, OnCompletedRead, null);

}

else

{

// 结束操作

Debug.WriteLine(\" 异步线程：读取文件结束\");

//读完，触发事件

OnIsReturnEvent();

//inputStream.Close();

}

}

}

public class ReturnEndReadEventargs : EventArgs

{

private bool isReturn;

public ReturnEndReadEventargs(bool isReturn)

{

this.isReturn = isReturn;

}

public bool IsReturn

{

get { return isReturn; }

set { isReturn = value; }

}

}

public delegate void ReturnEndEvent(object sender, ReturnEndReadEventargs args);

}