Should I use a Web API 2.2 custom filter or message handler?

Question

I am building a Web API service which will accept 2 of 4 possible tokens in the header. These tokens are used for different purposes but will all be able to be resolved (using lookup in a DB and other operations) to a couple of key pieces of user data.

Only a limited number of endpoints in my controllers will need to receive this information and so I need to know if I should be building a message handler (I believe this is executed for all requests) or a custom action filter (attached via attributes to the specific endpoints.)

Which method is most appropriate for retrieving data from the request header, using it to retrieve user information and populating the header/request with the retrieved data for the controller to use?

Answer 1

Token is an over-loaded term but if you are using "token" as in security token meant for authentication, you can create an authentication filter. If your tokens are just identifiers using which you pull more data from a data store, action filter is a good choice. As you said, message handlers run for all requests (per-route or global granularity) and may not be a good candidate. However, message handlers run earlier in the pipeline and action filters run just before the action method. So, in future, if any other component in your Web API pipeline needs this data, action filter could be too late. If you know for sure only controllers will ever need this data, action filter is probably the best place, given the granularity they provide.