ASP.NET利用HttpHandler实现多扩展名文件下载

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; }

}

}

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：

代码



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);
}
}

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：

代码



<system.web> <httpHandlers> <add verb="*" path="download.aspx" type="DownloadHandler" /> </httpHandlers> </system.web>

<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：

代码



<%@ 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>

<%@ 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：

代码



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;
}
}

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。:)