Changes for custom routing constraints in WebAPI 2.1

Question

Since I updated my WebAPI 2 apps to WebAPI 2.1, routing stopped working. I had a couple of custom routing constraints implemented as GuidConstraint. The exception I was receiving was the following:

System.InvalidOperationException: The constraint entry 'guid' on the route with route template '{guid}/{language}/{controller}/{id}' must have a string value or be of a type which implements 'System.Web.Http.Routing.IHttpRouteConstraint'.

This problem is not mentioned in documentation.

The following post has a purpose of a knowledge sharing and opinion exchange.

Was my previous implementation wrong? What changes in the new implementation in 2.1 that doesn't anymore support the more generic interface?

Answer 1

The solution is to implement IHttpRouteConstraint instead of IRouteConstraint on your custom routing constraint classes. The logic in most of the cases will stay the same.