ASP.NET利用HttpHandler实现多扩展名文件下载

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:


<%@ 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:


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。:)

源码下载:DownloadSolution.rar

 原文地址:http://www.cnblogs.com/liping13599168/archive/2009/02/08/1386111.html

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