ASP.NET Downloadable Image Files? - asp.net

Question

I don't have apache support on this website, but I need to be able to allow images to be downloadable in a certain directory only. How can I do this? This site only has ASP.NET support, and it's killing me! Noticed this link: How to download files in mvc3? but not sure where to put that code at, or even if that code there would help me any.
Any help would be greatly appreciated! A Starting point or something...
Is there a way I can just do this in HTML? Like, for example, set the download link to point to an html file, where the HTML file grabs the image file and makes it downloadable, in and of itself?
So far I have the following ASP code in a file called: default.asp
Which begins the download just fine, but it downloads an empty file (download.jpg). How can I point the following code to an actual image file to download?
<%# Language=VBScript %>
<% Option Explicit
Response.ContentType = "application/octet-stream"
Response.AddHeader "Content-Disposition", "attachment; filename=" + "download.jpg"
%>
I have a file named, "download.jpg" even within the same directory, but it never downloads the actual image. It downloads a 90 byte empty image file instead.
I even tried this with no luck:
<%# Language=VBScript %>
<% Option Explicit
Response.ContentType = "application/octet-stream"
Response.AddHeader "Content-Disposition","attachment; filename=07awardee.png"
Response.TransmitFile Server.MapPath("~/images/07awardee.png")
Response.End
%>
And yes, I have the 07awardee.png file in images/07awardee.png on the server root and even in the folder root where default.asp is located. Arggg! What gives here? The file is a bit bigger now at 392 bytes, but it still isn't readable as an image file... I've been searching the internet and this is supposed to work, but doesn't! What could be the problem here?

Answer 1

Your .aspx page with a Request.End throws a ThreadAbortException, and that's bad for server performance (too many of these can even crash a server). So you'll want to avoid that. http://weblogs.asp.net/hajan/archive/2010/09/26/why-not-to-use-httpresponse-close-and-httpresponse-end.aspx
The way I handle this problem is with a HttpHandler (.ashx) and use that to serve downloadable image files. I used some of your code because my implementation was in C# and has much more code (includes image scaling options etc):
//<%# WebHandler Language="VB" Class="DownloadImage" %> // uncomment this line!
Public Class DownloadImage : Implements IHttpHandler
Protected EnabledTypes() As String = New String() {".jpg", ".gif", ".png"}
Public Sub ProcessRequest(ByVal context As HttpContext) _
Implements IHttpHandler.ProcessRequest
Dim request = context.Request
If Not String.IsNullOrEmpty(request.QueryString("file")) Then
Dim path As String = context.Server.MapPath(request.QueryString("file"))
Dim file As System.IO.FileInfo = New System.IO.FileInfo(path)
If file.Exists And EnabledTypes.Contains(file.Extension.ToLower()) Then
context.Response.Clear()
context.Response.AddHeader("Content-Disposition", _
"attachment; filename=" & file.Name)
context.Response.AddHeader("Content-Length", file.Length.ToString())
context.Response.ContentType = "application/octet-stream"
context.Response.WriteFile(file.FullName)
Else
context.Response.ContentType = "plain/text"
context.Response.Write("This file does not exist.")
End If
Else
context.Response.Write("Please provide a file to download.")
End If
End Sub
Public ReadOnly Property IsReusable() As Boolean _
Implements IHttpHandler.IsReusable
Get
Return True
End Get
End Property
End Class
Make sure you implement a check for image files, otherwise you have a potential security problem. (Users could download web.config where database passwords are stored)
The link would become:
Download image

Answer 2

You should clear the header and provide the correct header and content type
Response.Clear()
Response.AppendHeader("Content-Disposition", "attachment; filename=somefilename")
Response.ContentType = "image/jpeg"
Response.TransmitFile(Server.MapPath("/xyz.jpg"));
Response.End();

Answer 3

OMG, I rock. Here's the way this is done. Create a file called, download.aspx, and input the following code into it:
<%# Page language="vb" runat="server" explicit="true" strict="true" %>
<script language="vb" runat="server">
Sub Page_Load(Sender As Object, E As EventArgs)
Dim strRequest As String = Request.QueryString("file")
If strRequest <> "" AND strRequest.EndsWith(".jpg") OR strRequest.EndsWith(".jpeg") OR strRequest.EndsWith(".png") OR strRequest.EndsWith(".gif") OR strRequest.EndsWith(".pdf") OR strRequest.EndsWith(".doc") OR strRequest.EndsWith(".docx") OR strRequest.EndsWith(".bmp") Then
Dim path As String = Server.MapPath(strRequest)
Dim file As System.IO.FileInfo = New System.IO.FileInfo(path)
If file.Exists Then
Response.Clear()
Response.AddHeader("Content-Disposition", "attachment; filename=" & file.Name)
Response.AddHeader("Content-Length", file.Length.ToString())
Response.ContentType = "application/octet-stream"
Response.WriteFile(file.FullName)
Response.End
Else
Response.Write("This file does not exist.")
End If
Else
Response.Write("You do not have permission to download this file type!")
End If
End Sub
</script>
Now, when you want to get a file to download (ANY FILE), just link it like so:
Download the logo image
And that's all she wrote!