How to get a piece of the Asp.net URL mvc5

Question

I have the following URL:

http://localhost:59278/video/categoria/desenho

I’m trying to use the Url.Action to mount a URL that is based on the value of the current URL. I need to take the amount desenho of the URL.

How can I do that:

Url.Action("Index","video",new { categoria = **????** }