ASP.NET利用HttpHandler实现多扩展名文件下载

￡神魔★判官ぃ 2022-08-07 04:52 161阅读 0赞

原文：[http://blog.itpub.net/12639172/viewspace-545679/][http_blog.itpub.net_12639172_viewspace-545679]

以前写过这样一篇文章（ASP.NET文件下载函数(好用的东东)），发现很多朋友询问，并且有时候会发生错误，今天我再重新更新一下，利用IHttpHandler来实现多扩展名文件下载，思路是这样：

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\#" 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][http_www.w3.org_TR_xhtml1_DTD_xhtml1-transitional.dtd]">

Default.aspx.cs代码如下：

Default.aspx.cs Code  
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。:)

[http_blog.itpub.net_12639172_viewspace-545679]: http://blog.itpub.net/12639172/viewspace-545679/
[http_www.w3.org_TR_xhtml1_DTD_xhtml1-transitional.dtd]: http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd
[http_www.w3.org_1999_xhtml]: http://www.w3.org/1999/xhtml