Question

Greetings!

I’ve created an APSX web form that returns a remote image based on some supplied parameters. It can be used like this:

<img src='/ImageGetter.aspx?param1=abc&param2=123' /> 

ImageGetter.aspx’s markup and code look similar to this:

<%@ OutputCache Duration='100000' VaryByParam='*' Location='ServerAndClient' %> <%@ Page Language='C#' AutoEventWireup='false' EnableSessionState='False' CodeBehind='ImageGetter.aspx.cs' Inherits='ACME.Helpers.ImageGetter' %> 

This code is called in ImageGetter.aspx’s Page_Load method:

byte[] data = null; Dictionary<string, string> file_locations = GetImageLocations(param1, param2); try {     data = new WebClient().DownloadData(file_locations['main']); } catch (WebException wex) {     try     {         data = new WebClient().DownloadData(file_locations['backup']);     }     catch (Exception e)     {         throw;     } } Response.ContentType = 'image/jpeg'; Response.OutputStream.Write(data, 0, data.Length); Response.End(); 

From my testing, it doesn’t appear to be caching. Is this possible to do with Output Caching or should I resort to writing my own cache to store the byte arrays depending on query string paramters?

Answer 1

Try dropping the Response.End() as this will terminate the thread prematurely and prevent output caching from taking place.

See: http://bytes.com/groups/net-asp/323363-cache-varybyparam-doesnt-work

You may wish to consider using an ASHX handler and using your own caching method.