用Visual C#實現文件下載功能(2)

下面就是程序的源代碼：

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Net;
using System.IO;
using System.Threading;

namespace MyGetCar
{
///
/// Form1 的摘要說明。
///
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Label label1;
private System.Windows.Forms.Label label2;
private System.Windows.Forms.TextBox srcAddress;
private System.Windows.Forms.TextBox tarAddress;
private System.Windows.Forms.StatusBar statusBar;
private System.Windows.Forms.Button Start;

private WebClient client = new WebClient();

///
/// 必需的設計器變量。
///
private System.ComponentModel.Container components = null;

public Form1()
{
//
// Windows 窗體設計器支持所必需的
//
InitializeComponent();

//
// TODO: 在 InitializeComponent 調用後添加任何構造函數代碼
//
}

///
/// 清理所有正在使用的資源。
///
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}

#region Windows Form Designer generated code
///
/// 設計器支持所需的方法 - 不要使用代碼編輯器修改
/// 此方法的內容。
///
private void InitializeComponent()
{
this.label1 = new System.Windows.Forms.Label();
this.label2 = new System.Windows.Forms.Label();
this.srcAddress = new System.Windows.Forms.TextBox();
this.tarAddress = new System.Windows.Forms.TextBox();
this.statusBar = new System.Windows.Forms.StatusBar();
this.Start = new System.Windows.Forms.Button();
this.SuspendLayout();
//
// label1
//
this.label1.Location = new System.Drawing.Point(8, 32);
this.label1.Name = "label1";
this.label1.Size = new System.Drawing.Size(72, 23);
this.label1.TabIndex = 0;
this.label1.Text = "文件地址：";
this.label1.TextAlign = System.Drawing.ContentAlignment.MiddleRight;
//
// label2
//
this.label2.Location = new System.Drawing.Point(8, 72);
this.label2.Name = "label2";
this.label2.Size = new System.Drawing.Size(72, 23);
this.label2.TabIndex = 1;
this.label2.Text = "另存到：";
this.label2.TextAlign = System.Drawing.ContentAlignment.MiddleRight;
//
// srcAddress
//
this.srcAddress.Location = new System.Drawing.Point(80, 32);
this.srcAddress.Name = "srcAddress";
this.srcAddress.Size = new System.Drawing.Size(216, 21);
this.srcAddress.TabIndex = 2;
this.srcAddress.Text = "";
//
// tarAddress
//
this.tarAddress.Location = new System.Drawing.Point(80, 72);
this.tarAddress.Name = "tarAddress";
this.tarAddress.Size = new System.Drawing.Size(216, 21);
this.tarAddress.TabIndex = 3;
this.tarAddress.Text = "";
//
// statusBar
//
this.statusBar.Location = new System.Drawing.Point(0, 151);
this.statusBar.Name = "statusBar";
this.statusBar.Size = new System.Drawing.Size(312, 22);
this.statusBar.TabIndex = 4;
//
// Start
//
this.Start.FlatStyle = System.Windows.Forms.FlatStyle.Flat;
this.Start.Location = new System.Drawing.Point(216, 112);
this.Start.Name = "Start";
this.Start.Size = new System.Drawing.Size(75, 24);
this.Start.TabIndex = 5;
this.Start.Text = "開始下載";
this.Start.Click += new System.EventHandler(this.Start_Click);
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
this.ClientSize = new System.Drawing.Size(312, 173);
this.Controls.AddRange(new System.Windows.Forms.Control[] {
this.Start,
this.statusBar,
this.tarAddress,
this.srcAddress,
this.label2,
this.label1});
this.MaximizeBox = false;
this.Name = "Form1";
this.Text = "文件下載器";
this.ResumeLayout(false);

}
#endregion

///
/// 應用程序的主入口點。
///
[STAThread]
static void Main()
{
Application.Run(new Form1());
}

private void StartDownload()
{
Start.Enabled = false;
string URL = srcAddress.Text;
int n = URL.LastIndexOf(/);
string URLAddress = URL.Substring(0,n);
string fileName = URL.Substring(n+1,URL.Length-n-1);
string Dir = tarAddress.Text;
string Path = Dir+\+fileName;

try
{
WebRequest myre=WebRequest.Create(URLAddress);
}
catch(WebException exp)
{
MessageBox.Show(exp.Message,"Error");
}

try
{
statusBar.Text = "開始下載文件...";
client.DownloadFile(URLAddress,fileName);
Stream str = client.OpenRead(URLAddress);
StreamReader reader = new StreamReader(str);
byte[] mbyte = new byte[100000];
int allmybyte = (int)mbyte.Length;
int startmbyte = 0;
statusBar.Text = "正在接收數據...";
while(allmybyte>0)
{
int m = str.Read(mbyte,startmbyte,allmybyte);
if(m==0)
break;

startmbyte+=m;
allmybyte-=m;
}

FileStream fstr = new FileStream(Path,FileMode.OpenOrCreate,FileAccess.Write);
fstr.Write(mbyte,0,startmbyte);
str.Close();
fstr.Close();

statusBar.Text = "下載完畢！";
}
catch(WebException exp)
{
MessageBox.Show(exp.Message,"Error");
statusBar.Text = "";
}

Start.Enabled = true;
}

private void Start_Click(object sender, System.EventArgs e)
{
Thread th = new Thread(new ThreadStart(StartDownload));
th.Start();
}
}
} 　　

　　四、總結

　　以上我通過一個實例向大家展示了如何用Visual C#實現網絡文件的下載，我們不難發現用Visual C#進行Internet通訊編程是非常方便的。

　　在上面的程序中，我們僅僅用到了WebClient類的一些方法，而WebClient類不光提供了網絡文件下載的方法，還提供了文件上傳的方法，有興趣的讀者不妨一試――用之實現一個文件上傳器。

　　同時這個程序只是一個非常簡單的例子，程序下載完一個網頁後，它所獲得的僅僅是主頁面的內容，並不能獲得其中的圖片、CSS等文件，所以要做出一個比較好的文件下載器還需讀者進一步改進之。