1. 首先新建一个用于进行下载处理的page页,如download.aspx,里面什么东西也没有。
2. 添加一个DownloadHandler类,它继承于IHttpHandler接口,可以用来自定义HTTP 处理程序同步处理HTTP的请求。public class DownloadHandler : IHttpHandler{ public void ProcessRequest(HttpContext context){ HttpResponse Response = context.Response;HttpRequest Request = context.Request;System.IO.Stream iStream = null;byte[] buffer = new Byte[10240];int length;long dataToRead;try{ string filename = FileHelper.Decrypt(Request["fn"]); //通过解密得到文件名string filepath = HttpContext.Current.Server.MapPath("~/") + "files/" + filename; //待下载的文件路径iStream = new System.IO.FileStream(filepath, System.IO.FileMode.Open,System.IO.FileAccess.Read, System.IO.FileShare.Read);Response.Clear();dataToRead = iStream.Length;long p = 0;if (Request.Headers["Range"] != null){ Response.StatusCode = 206;p = long.Parse(Request.Headers["Range"].Replace("bytes=", "").Replace("-", ""));}if (p != 0){ Response.AddHeader("Content-Range", "bytes " + p.ToString() + "-" + ((long)(dataToRead - 1)).ToString() + "/" + dataToRead.ToString());}Response.AddHeader("Content-Length", ((long)(dataToRead - p)).ToString());Response.ContentType = "application/octet-stream";Response.AddHeader("Content-Disposition", "attachment; filename=" + System.Web.HttpUtility.UrlEncode(System.Text.Encoding.GetEncoding(65001).GetBytes(Path.GetFileName(filename))));iStream.Position = p;dataToRead = dataToRead - p;while (dataToRead > 0){ if (Response.IsClientConnected){ length = iStream.Read(buffer, 0, 10240);Response.OutputStream.Write(buffer, 0, length);Response.Flush();buffer = new Byte[10240];dataToRead = dataToRead - length;}else{ dataToRead = -1;}}}catch (Exception ex){ Response.Write("Error : " + ex.Message);}finally{ if (iStream != null){ iStream.Close();}Response.End();}}public bool IsReusable{ get { return true; }}}3. 这里涉及到一个文件名加解密的问题,是为了防止文件具体名称暴露在状态栏中,所以添加一个FileHelper类,代码如下:public class FileHelper{ public static string Encrypt(string filename){ byte[] buffer = HttpContext.Current.Request.ContentEncoding.GetBytes(filename);return HttpUtility.UrlEncode(Convert.ToBase64String(buffer));}public static string Decrypt(string encryptfilename){ byte[] buffer = Convert.FromBase64String(encryptfilename);return HttpContext.Current.Request.ContentEncoding.GetString(buffer);}}利用Base64码对文件名进行加解密处理。4. 在Web.config上,添加httpHandlers结点,如下:<system.web><httpHandlers><add verb="*" path="download.aspx" type="DownloadHandler" /></httpHandlers></system.web>5. 现在新建一个aspx页面,对文件进行下载:Default.aspx代码如下:Default.aspx Code<%@ Page Language="C#" CodeFile="Default.aspx.cs" Inherits="_Default" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" ><head runat="server"><title>文件下载</title></head><body><form id="form1" runat="server"><div><asp:HyperLink ID="link" runat="server" Text="文件下载"></asp:HyperLink></div></form></body></html>Default.aspx.cs代码如下:Default.aspx.cs Codeusing System;using System.Data;using System.Configuration;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;public partial class _Default : System.Web.UI.Page{ protected void Page_Load(object sender, EventArgs e){ string url = FileHelper.Encrypt("DesignPattern.chm");link.NavigateUrl = "~/download.aspx?fn=" + url;}}