How to make IRouteConstraint filter route
Here's a simple constraint that looks up an article slug in a fictional repository:
public class SlugRouteConstraint : IRouteConstraint{ private readonly ISlugRepository slugRepository = new SlugRepository(); public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection) { if (!values.ContainsKey(parameterName)) return false; var slug = (string)values[parameterName]; return slugRepository.Exists(slug); }}You could wire up the constraint like this:
routes.MapRoute("Slugs", "{slug}", new { controller = "Articles", action = "View" }, new { slug = new SlugConstraint() });