URL rewrite + outputcache

Question

I've got a problem using outputcache together with urlrewriting. We've got an application that rewrites url (IE http://localhost/about/ ) to "~/page.aspx". Based on the URL (/about/) we figure out which content to show.

Now we're trying to add outputcache to that page:

< %@ outputcache duration="600" location="Server" varybyparam="Custom" varybycustom="RawURL" %>

And in the Global.asax we override GetVaryByCustomString like below:

public override string GetVaryByCustomString(HttpContext context, string custom)
{
    if (custom == "RawUrl")
    {
        return context.Request.RawUrl;
    }
    else
    {
        return string.Empty;
    }
}

However, when we publish the page i'd like to invalidate the cache so that the editors see the change directly. But no matter what I try, I cannot seem to invalidate the cache. If I'd like to invalidate "/about/" I would like to do this:

HttpResponse.RemoveOutputCacheItem("/about/");

That doesn't work unfortunately. The only thing that seems to work is:

HttpResponse.RemoveOutputCacheItem("/page.aspx");

This clears the cache for all my pages, not just "/about/".

Is there any way to invalidate the cache based on the url? Or should we provide a cache key or something per page to be able to invalidate the cache programmatically?

Thanks in advance!

Answer 1

I've solved with using following link. http://www.superstarcoders.com/blogs/posts/making-asp-net-output-cache-work-with-post-back.aspx

Basically on my usercontrol;

protected override void OnInit(EventArgs e)
    {
        base.OnInit(e);

        if (Request.QueryString["url"] == null)
            return;
        string url = "www." + Request.QueryString["url"].ToString().Replace("http://", "").Replace("https://", "").Replace("www.", "").ToLower();


        Response.AddCacheItemDependency(url);
    }

Answer 2

You don't need to invalidate the cache. You can tell the server to not use the cache for certain requests.

To do this in your page load add this

Response.Cache.AddValidationCallback((ValidateCache), Session);

Then add this method to tell app whether use what is in the output cache for the current request

    public static void ValidateCache(HttpContext context, Object data, ref HttpValidationStatus status)
    {

        bool isEditor = /*assignment here*/;
        if (!isEditor)
        {
            status = HttpValidationStatus.Valid;
        }
        else
        {
            status = HttpValidationStatus.IgnoreThisRequest;
        }
    }

If you do not want a certain request to be cached for other users to see use the following

 Response.Cache.SetCacheability(HttpCacheability.NoCache);