1. Create a page for download processing, such as download. aspx. There is nothing in it.
2. Add a DownloadHandler class that inherits from the IHttpHandler interface. You can use a custom HTTP handler to synchronously process HTTP requests.
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"]); // obtain the file name through decryption
String filepath = HttpContext. Current. Server. MapPath ("~ /") +" Files/"+ filename; // path of the file to be downloaded
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 (1, 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. The file name encryption and decryption problem is involved here. To prevent the file name from being exposed to the status bar, add a FileHelper class. The Code is as follows:
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 );
}
}
Use Base64 to encrypt and decrypt the file name.
4. On Web. config, add the httpHandlers node as follows:
<System. web>
<HttpHandlers>
<Add verb = "*" path = "download. aspx" type = "DownloadHandler"/>
</HttpHandlers>
</System. web>
5. Create An aspx page to download the file:
The Default. aspx code is as follows:
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">
<Html xmlns = "http://www.w3.org/1999/xhtml">
<Head runat = "server">
<Title> File Download </title>
</Head>
<Body>
<Form id = "form1" runat = "server">
<Div>
<Asp: HyperLink ID = "link" runat = "server" Text = "File Download"> </asp: HyperLink>
</Div>
</Form>
</Body>
</Html>
The Default. aspx. cs code is as follows:
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;
}
}
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