Question

I am trying to create a route constraint but not sure what would be the best for this. Here is the route with no constraint :

context.MapRoute(
    "Accommodation_accomm_tags",
    "accomm/{controller}/{action}/{tag}",
    new { action = "Tags", controller = "AccommProperty" },
    new { tag = @"" } //Here I would like to put a RegEx for not null match
);

What would be the best solution for this?

Answer 1

Why do you need a constraint for a not null/empty match? Normally if you define your route like this:

context.MapRoute(
    "Accommodation_accomm_tags",
    "accomm/{controller}/{action}/{tag}",
    new { action = "Tags", controller = "AccommProperty" },
);

and tag is not specified in the request url this route simply won’t match.

And if you want a token to be optional, then:

context.MapRoute(
    "Accommodation_accomm_tags",
    "accomm/{controller}/{action}/{tag}",
    new { action = "Tags", controller = "AccommProperty", tag = UrlParameter.Optional },
);

Constraints are used when you want to constrain the value of a given route token to some specific format.