利用HttpHandler实现多扩展名文件下载代码,Asp.Net代码库,德仔网

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【Asp.Net】利用HttpHandler实现多扩展名文件下载
作者:Dezai.CN / 发布于2013/11/4/ 455

	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。

	<!--

	Code highlighting produced by Actipro CodeHighlighter (freeware)
	http://www.CodeHighlighter.com/

	-->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：

	<!--

	Code highlighting produced by Actipro CodeHighlighter (freeware)
	http://www.CodeHighlighter.com/

	-->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：

	<!--

	Code highlighting produced by Actipro CodeHighlighter (freeware)
	http://www.CodeHighlighter.com/

	--><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
	<!--

	Code highlighting produced by Actipro CodeHighlighter (freeware)
	http://www.CodeHighlighter.com/

	--><%@ Page Language="C#" AutoEventWireup="true" 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 Code
	<!--

	Code highlighting produced by Actipro CodeHighlighter (freeware)
	http://www.CodeHighlighter.com/

	-->using 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;
	 }
	}
	这样就实现了文件下载时,不管是什么格式的文件,都能够弹出打开/保存窗口。:)
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