In ASP.NET, is it possible to output cache by host name? ie varybyhost or varbyhostheader?

Question

Hi folks,

I've got a website that has a number of host headers. Depending on the host header, the results are different - both visually (theme'd) and data.

So lets imagine i have a website called 'Foo' - that returns search results (original, eh?).

Now, the same code runs both sites. It is physically the same server/website (using Host Headers) :-

1. www.foo.com
2. www.foo.com.au

Now, if i goto '.com', the site is theme'd in blue. if i goto the '.com.au' site, it's theme'd in red.

And the data is different for the same search result, based on the host name (ie. us results for .com, au results for .com.au)

SO .. if i wish to use OutputCaching .. can this be handled / differ by the host name?

I don't want to have the first person goto the .com site .. grab the results ... and the a second person goto my .com.au .. same search data .. and get the theme and results for the .com site.

Possible?

Answer 1

Check out the VaryByCustom parameter of the OutputCache directive.

To define what happens when VaryByCustom is called, you need to override the method GetVaryByCustomString:

public override string GetVaryByCustomString(HttpContext context, string custom)
{
    if(custom == "Your_Custom_Value")
    {
        // Do some validation.
        // Return a string for say, .com, or .com.au

    }
    return String.Empty;
}

The key is to return a string value for each instance you want to cache. In your case, your overrided method would need to strip the ".com" or ".com.au" part from the URL and return it. Each different value produces a different cache.

HTH