mysql实现异步读取文件_文件异步操作的实现

异步操作可以使我们的程序获得更优的性能&＃xff0c;特别是对大文件进行处理时&＃xff0c;这一点相信大家都知道。这里我写了一个示例。希望能给大家一个帮助。

using System.IO;

using System.Threading;

public class Form2 : System.Windows.Forms.Form

{

private System.Windows.Forms.Button button1;

private System.Windows.Forms.TextBox textBox1;

private System.Windows.Forms.ProgressBar progressBar1;

FileStream fs&＃61;null;

FileStream fsW&＃61;new FileStream("C://a.exe",FileMode.Create,FileAccess.Write,FileShare.Read);

int bufferLenth&＃61;1024*64;//将缓冲区定义为最少64k&＃xff0c;在WIN平台上有很大的性能提高(性能分界线)

AsyncCallback cb&＃61;null;

byte[] bs&＃61;new byte[1024*64];

private System.Windows.Forms.TextBox textBox2;

///

/// 必需的设计器变量。

///

private System.ComponentModel.Container components &＃61; null;

public Form2()

{

//

// Windows 窗体设计器支持所必需的

//

InitializeComponent();

//

// TODO: 在 InitializeComponent 调用后添加任何构造函数代码

//

}

///

/// 应用程序的主入口点。

///

[STAThread]

static void Main()

{

Application.Run(new Form2());

}

///

/// 清理所有正在使用的资源。

///

protected override void Dispose( bool disposing )

{

if( disposing )

{

if(components !&＃61; null)

{

components.Dispose();

}

}

base.Dispose( disposing );

}

#region Windows 窗体设计器生成的代码

///

/// 设计器支持所需的方法 - 不要使用代码编辑器修改

/// 此方法的内容。

///

private void InitializeComponent()

{

this.button1 &＃61; new System.Windows.Forms.Button();

this.textBox1 &＃61; new System.Windows.Forms.TextBox();

this.progressBar1 &＃61; new System.Windows.Forms.ProgressBar();

this.textBox2 &＃61; new System.Windows.Forms.TextBox();

this.SuspendLayout();

//

// button1

//

this.button1.Location &＃61; new System.Drawing.Point(368, 40);

this.button1.Name &＃61; "button1";

this.button1.Size &＃61; new System.Drawing.Size(136, 40);

this.button1.TabIndex &＃61; 0;

this.button1.Text &＃61; "button1";

this.button1.Click &＃43;&＃61; new System.EventHandler(this.button1_Click);

//

// textBox1

//

this.textBox1.Location &＃61; new System.Drawing.Point(120, 48);

this.textBox1.Name &＃61; "textBox1";

this.textBox1.Size &＃61; new System.Drawing.Size(232, 21);

this.textBox1.TabIndex &＃61; 1;

this.textBox1.Text &＃61; "E://tools//CHS_MSDE2000A.exe";

//上面这个文件可以换掉&＃xff0c;最好大一点的文件.

//

// progressBar1

//

this.progressBar1.Location &＃61; new System.Drawing.Point(72, 112);

this.progressBar1.Name &＃61; "progressBar1";

this.progressBar1.Size &＃61; new System.Drawing.Size(632, 40);

this.progressBar1.TabIndex &＃61; 2;

//

// textBox2

//

this.textBox2.Location &＃61; new System.Drawing.Point(56, 168);

this.textBox2.Multiline &＃61; true;

this.textBox2.Name &＃61; "textBox2";

this.textBox2.ScrollBars &＃61; System.Windows.Forms.ScrollBars.Vertical;

this.textBox2.Size &＃61; new System.Drawing.Size(648, 272);

this.textBox2.TabIndex &＃61; 3;

this.textBox2.Text &＃61; "";

//

// Form2

//

this.AutoScaleBaseSize &＃61; new System.Drawing.Size(6, 14);

this.ClientSize &＃61; new System.Drawing.Size(736, 485);

this.Controls.Add(this.textBox2);

this.Controls.Add(this.progressBar1);

this.Controls.Add(this.textBox1);

this.Controls.Add(this.button1);

this.Name &＃61; "Form2";

this.Text &＃61; "Form2";

this.ResumeLayout(false);

}

#endregion

private void button1_Click(object sender, System.EventArgs e)

{

//这个文件最好大一点

string fName &＃61;this.textBox1.Text;

//使用异步读取。缓冲区最好大于64k.不然性能更低

fs&＃61;new FileStream(fName,FileMode.Open,FileAccess.Read,FileShare.ReadWrite,bufferLenth,true);

cb&＃61;new AsyncCallback(ShowText);

this.progressBar1.Maximum&＃61;(int)fs.Length;

fs.BeginRead(bs,0,bufferLenth,cb,fs);

//开始异步读取文件

}

//异步回调的实现函数,当缓冲区数据读完毕后

public void ShowText(IAsyncResult result)

{

int rb&＃61;fs.EndRead(result);//获取最终得到的数据量。不一定是64*1024。最后一次可能小于这个数

fsW.Write(bs,0,rb);//将读到的数据写入到别一个地方。

this.progressBar1.Value&＃61;(int)(fs.Position);//设置进度条

if(rb

{

fsW.Flush();

fsW.Close();

fs.Close();

return;

}

fs.BeginRead(bs,0,bufferLenth,cb,fs);//如果还有数据再次读取64*1024字节

}