How to determine total size of ASP.Net cache?

I’m using the ASP.net cache in a web project, and I’m writing a “status” page for it which shows the items in the cache, and as many statistics about the cache as I can find. Is there any way that I can get the total size (in bytes) of the cached data? The size of each item would be even better. I want to display this on a web page, so I don’t think I can use a performance counter.

Performance Counter – System.InvalidOperationException: Category does not exist

I have following class that returns number of current Request per Second of IIS. I call RefreshCounters every minute in order to keep Requests per Second value refreshed (because it is average and if I keep it too long old value will influence result too much)… and when I need to display current RequestsPerSecond I call that property.

Get Performance Counter Instance Name (w3wp#XX) from ASP.NET worker process ID

I would like to display some memory statistics (working set, GCs etc.) on a web page using the .NET/Process performance counters. Unfortunately, if there are multiple application pools on that server, they are differentiated using an index (#1, #2 etc.) but I don’t know how to match a process ID (which I have) to that #xx index. Is there a programmatic way (from an ASP.NET web page)?