using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

public class WebForm1 : System.Web.UI.Page
{
 private void Page_Load(object sender, System.EventArgs e)
 {

  string s  = @"e:\northwind.mdb";
  s = @"I:\\SetupRes\\Sun\\j2re-1_4_2_05-windows-i586-p.exe";
  System.IO.Stream S = new System.IO.FileStream(s, System.IO.FileMode.Open, System.IO.FileAccess.Read,System.IO.FileShare.Read);

  long p = 0;

  long l = new System.IO.FileInfo(s).Length;

  if (Request.Headers["Range"] != null)
  {
   Response.StatusCode = 206;
   p = long.Parse( Request.Headers["Range"].Replace("bytes=","").Replace("-",""));
  }

  Response.AddHeader("Content-Length", ((long)(l - p)).ToString()  );

  if (p != 0)
  {
   //不是从最开始下载,
   //响应的格式是:
   //Content-Range: bytes [文件块的开始字节]-[文件的总大小 - 1]/[文件的总大小]
   Response.AddHeader("Content-Range","bytes " + p.ToString() + "-" + ((long)(l - p)).ToString() + "/" + l.ToString());
  }

  Response.ContentType = "application/octet-stream";   
  Response.AddHeader("Content-Disposition", "attachment; filename="  +  System.IO.Path.GetFileName(s));

  S.Position = p;

  int i = 1;
  byte[] b = new Byte[1024];
  while (i > 0)
  {
   i = S.Read(b, 0, b.Length);
   Response.OutputStream.Write(b, 0, i);
  }

  S.Close();
  Response.End();
 }
 #region Web 窗体设计器生成的代码
 override protected void OnInit(EventArgs e)
 {
  //
  // CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
  //
  InitializeComponent();
  base.OnInit(e);
 }
 
 ///
 /// 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.Load += new System.EventHandler(this.Page_Load);
 }
 #endregion
}