用webclient和stream下载文件的问题。
大家好，我昨天开始学习.net，看了几个示例程序，有如下一个问题请教：
程序员不说2话，翠花！上代码！
---------------------------------------------
//就一个form
//textBox1 文本提示，textBox2 下载URL textBox3 保存位置 btnUpdate 启动下载 btnExit 退出。
//完成功能：用户输入URL于textBox2中，输入保存位置 比如D: 在 textBox3 中
//点 下载 按钮，另开一个线程进行下载。
//问：如何实现边下载边保存？我开了一个100kb的缓冲区，但大于此数字的文件也只取这么多。
//本人水平非常有限，从下载按钮后执行的操作即可看出，那几个对话框是为了了解MessageBox的用法
//200分奖励。本程序为自己学习之用。
//以下是代码。
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Net;//网络相关
using System.IO;
using System.Threading;
namespace Shiying.Inheritance
{
/// <summary>
/// Form1 的摘要说明。
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.GroupBox groupBox1;
private System.Windows.Forms.TextBox textBox1;
private System.Windows.Forms.Button btnExit;
private System.Windows.Forms.Button btnUpdate;
private System.Windows.Forms.Label label1;
private System.Windows.Forms.TextBox textBox2;
private System.Windows.Forms.Label label2;
private System.Windows.Forms.TextBox textBox3;
/// <summary>
/// 必需的设计器变量。
/// </summary>
private System.ComponentModel.Container components = null;
public Form1()
{
//
// 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
//
}
/// <summary>
/// 清理所有正在使用的资源。
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows 窗体设计器生成的代码
/// <summary>
/// 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。
/// </summary>
private void InitializeComponent()
{
this.groupBox1 = new System.Windows.Forms.GroupBox();
this.textBox1 = new System.Windows.Forms.TextBox();
this.btnUpdate = new System.Windows.Forms.Button();
this.btnExit = new System.Windows.Forms.Button();
this.label1 = new System.Windows.Forms.Label();
this.textBox2 = new System.Windows.Forms.TextBox();
this.label2 = new System.Windows.Forms.Label();
this.textBox3 = new System.Windows.Forms.TextBox();
this.groupBox1.SuspendLayout();
this.SuspendLayout();
//
// groupBox1
//
this.groupBox1.Controls.Add(this.textBox1);
this.groupBox1.Location = new System.Drawing.Point(8, 8);
this.groupBox1.Name = "groupBox1";
this.groupBox1.Size = new System.Drawing.Size(464, 232);
this.groupBox1.TabIndex = 0;
this.groupBox1.TabStop = false;
this.groupBox1.Text = "系统提示：";
//
// textBox1
//
this.textBox1.Location = new System.Drawing.Point(16, 24);
this.textBox1.Multiline = true;
this.textBox1.Name = "textBox1";
this.textBox1.ReadOnly = true;
this.textBox1.Size = new System.Drawing.Size(432, 192);
this.textBox1.TabIndex = 0;
this.textBox1.Text = "textBox1";
//
// btnUpdate
//
this.btnUpdate.Location = new System.Drawing.Point(296, 328);
this.btnUpdate.Name = "btnUpdate";
this.btnUpdate.Size = new System.Drawing.Size(80, 32);
this.btnUpdate.TabIndex = 1;
this.btnUpdate.Text = "下载";
this.btnUpdate.Click += new System.EventHandler(this.button1_Click);
//
// btnExit
//
this.btnExit.Location = new System.Drawing.Point(392, 328);
this.btnExit.Name = "btnExit";
this.btnExit.Size = new System.Drawing.Size(80, 32);
this.btnExit.TabIndex = 2;
this.btnExit.Text = "退出";
this.btnExit.Click += new System.EventHandler(this.button2_Click);
//
// label1
//
this.label1.Location = new System.Drawing.Point(8, 264);
this.label1.Name = "label1";
this.label1.Size = new System.Drawing.Size(80, 16);
this.label1.TabIndex = 3;
this.label1.Text = "下载位置：";
//
// textBox2
//
this.textBox2.Location = new System.Drawing.Point(88, 264);
this.textBox2.Name = "textBox2";
this.textBox2.Size = new System.Drawing.Size(384, 21);
this.textBox2.TabIndex = 4;
this.textBox2.Text = "textBox2";
//
// label2
//
this.label2.Location = new System.Drawing.Point(8, 296);
this.label2.Name = "label2";
this.label2.Size = new System.Drawing.Size(80, 16);
this.label2.TabIndex = 5;
this.label2.Text = "保存位置：";
//
// textBox3
//
this.textBox3.Location = new System.Drawing.Point(88, 296);
this.textBox3.Name = "textBox3";
this.textBox3.Size = new System.Drawing.Size(384, 21);
this.textBox3.TabIndex = 6;
this.textBox3.Text = "textBox3";
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
this.ClientSize = new System.Drawing.Size(480, 373);
this.Controls.Add(this.textBox3);
this.Controls.Add(this.label2);
this.Controls.Add(this.textBox2);
this.Controls.Add(this.label1);
this.Controls.Add(this.btnExit);
this.Controls.Add(this.btnUpdate);
this.Controls.Add(this.groupBox1);
this.Name = "Form1";
this.Text = "国研网在线更新系统.Net";
this.Load += new System.EventHandler(this.Form1_Load);
this.groupBox1.ResumeLayout(false);
this.ResumeLayout(false);
}
#endregion
/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
private void button2_Click(object sender, System.EventArgs e)
{
Application.Exit();
}
private void button1_Click(object sender, System.EventArgs e)
{
//取对话框的值,Yes/No
System.Windows.Forms.DialogResult rs;
rs=MessageBox.Show("LiveUpdate.Net开始更新","Liveupdate.net",MessageBoxButtons.YesNo);
if (rs.ToString()=="Yes")
{
MessageBox.Show("you click yes!");
Thread th = new Thread(new ThreadStart(DownloadFile));
th.Start();}
else if (rs.ToString()=="No") MessageBox.Show ("you click no!");
else
MessageBox.Show("Another key pressed!");
}
private void Form1_Load(object sender, System.EventArgs e)
{
}
private void DownloadFile()
{
btnUpdate.Enabled = false;
string URL = textBox2.Text ;
//取文件名字,最后一个/之后的就是文件名字
int n = URL.LastIndexOf('/');
string URLAddress = URL.Substring(0,n);
string fileName = URL.Substring(n+1,URL.Length-n-1);
string Dir = textBox3.Text;
string Path = Dir+'\\'+fileName;
try
{
WebRequest myre=WebRequest.Create(URLAddress);
}
catch(WebException exp)
{
MessageBox.Show(exp.Message,"Error");
}
try
{
System.Net.WebClient client=new WebClient();
textBox1.Text = "开始下载文件...";
client.DownloadFile(URL,fileName);
Stream str = client.OpenRead(URL);
StreamReader reader = new StreamReader(str);
byte[] mbyte = new byte[100000];
int allmybyte = (int)mbyte.Length;
int startmbyte = 0;
textBox1.Text = "正在接收数据...";
FileStream fstr = new FileStream(Path,FileMode.Append,FileAccess.Write);//Append只能和写一起用。
while(allmybyte>0)
{
int m = str.Read(mbyte,startmbyte,allmybyte);
if(m==0)
break;
fstr.Write(mbyte,0,startmbyte);
startmbyte+=m;
allmybyte-=m;
}
str.Close();
fstr.Close();
textBox1.Text = "下载完毕！";
}
catch(WebException exp)
{
MessageBox.Show(exp.Message,"Error");
textBox1.Text = "";
}
btnUpdate.Enabled = true;
}
}
}
问题点数：100、回复次数：6Top
1 楼51dianying（）回复于 2004-12-03 22:35:37 得分 0
不好意思，没想到最多只能给100分。呵呵。Top
2 楼cnhgj（戏子) (没时间练太极）回复于 2004-12-03 23:07:36 得分 0
http://search.csdn.net/Expert/topic/1809/1809756.xml?temp=.5159571Top
3 楼OneDotRed（武装到眼神）回复于 2004-12-04 14:23:28 得分 100
因为1.x的WebClient类没有异步方法，使用WebClient无法实现你所说的，在我的Blog(http://blog.csdn.net/onedotred)中有篇文章，讲的是使用C#异步读取文件。
其方法是，先获取流的大小，然后按照一小段一小段读取，写至磁盘上。和你的这个问题相似。
对于你的这个问题，可以这样解决,使用HttpWebRequest和HttpWebResponse类，获取HttpWebResponse的ContentLength，HttpWebResponse.GetResponseStream()获得流，其他的就和异步读取文件一样了。
Top
4 楼MyXQ（重剑）回复于 2004-12-14 09:29:22 得分 0
markTop
5 楼tangxiaogang510（一起同行）回复于 2005-04-10 15:13:13 得分 0
upTop
6 楼tangxiaogang510（一起同行）回复于 2005-04-11 19:36:48 得分 0
如果是B/S的话，你这样只能下载到WEB本地电脑里面，却不能下载到客户端，Top
