Asp .net mvc simple image switch

I am new to mvc and i have a 6 screenshots. On my page I show one screenshot and I have a back and next link that link /screenshots/+ for forward and /screenshots/-. Now I need a variable to keep track of which screenshot the users at but I have a minor understanding of mvc. I was thinking of using Application variable but that would be for all users. How would I keep a create a new variable for each person, the variables scope would only be for that page, asoon as the person goes to another page it would be gone, but I need to keep it for: /screenshots/+ and - which is captured by my controller with a string id.