ASP.NET 4 Unleashed

Using Constrained Routes

For a lot of situations, the type of route patterns that we have discussed thus far are sufficient. If you want static routes, or routes with simple parameters (with or without defaults), you are all set.

However, if you want to further constrain your route patterns so that only after certain conditions are met should your route be invoked, you’re also in luck. One of the overloads of the MapPageRoute method that we haven’t yet discussed actually takes a dictionary of constraints to route parameters. These constraints come in the form of regular expressions. (We warned you earlier that we’d have to talk about them eventually.)

At their simplest level you can use these regular expressions to limit the size of parameters ...