C# get url parameter namevaluecollection from rewritten url

Question

If the url is not rewritten say like this

&tag=sql&page=3

I would get the parameter collection like this

var parameters = HttpUtility.ParseQueryString(uri.Query);

But if I have something like this

/tag/sql-i/page/3/

That doesn't work.

What would be the best way to achieve the same result with a rewritten url?

Thanks