ASP.Net MVC has a powerful Routing Engine that allows mapping between URL Routes and Controller Actions. Below are few links regarding how you can control how browser requests match routes by creating route constraints. You use route constraints to restrict the browser requests that match a particular route.

• Creating a Route Constraint @ www.ASP.Net/MVC
  • http://www.asp.net/mvc/tutorials/controllers-and-routing/creating-a-route-constraint-cs
  • http://www.asp.net/mvc/tutorials/controllers-and-routing/creating-a-custom-route-constraint-cs
• Routing in ASP.NET Web API @ www.ASP.Net/web-api
  • http://www.asp.net/web-api/overview/web-api-routing-and-actions/routing-in-aspnet-web-api
• ASP.Net MVC Route Constraints @ Guy Burstein's Blog
  • http://blogs.microsoft.co.il/blogs/bursteg/archive/2009/01/11/asp-net-mvc-route-constraints.aspx
• Create Custom Route Constraints @ Stephen Walther’s Blog
  • http://stephenwalther.com/archive/2008/08/07/asp-net-mvc-tip-30-create-custom-route-constraints.aspx