Sure Let assume that I am having a website. I want to use Filters to customise the site. In these Filters i want to know whether a resource requested for is available or not. Suppose you type a bad url to my site I want to check for resource in the filter then pop appropriate message.
I didn't get you. Why you want to check in filters whether the resource is available or not. you just follow the asusual flow and if resource is not available , direct it to specific page with message.
As I m not able to think the benefit of checking resource availability in filters.
Chop your own wood, and it will warm you twice. - Henry Ford