Exposing taxonomy field in Sitefinity OData service

Sitefinity OData services and the Client SDK are great, but still lacking some generic functionality and documentation.
A good chance for me to blog a bit on this topic.

Classifications for an item are something I often need. 

But they are not so easy to expand.
The $expand is not working, nor does $select, nor selecting it in the webservices.config.

Actually - they work, but all you get is the Id of the taxonomy, so you will have to do a separate query to ask for the details. This gets quite complex (and inefficient) if you have a list of items to resolve for, or a few different types of taxonomies (I.promise() it can be a lot easier using the approach bellow, reducing your callbacks a bit :)).


I often use it to see if there is an undocumented functionality (and how things work in general).

With some digging I found that there is a type: "Telerik.Sitefinity.Web.Services.Contracts.TaxonomyRelationResolver". 
A brief look at the code confirms it is what we need.

We have everything we need to do this:

  • Go to Advanced Settings => Web Services => [Your Service] => Types => [Your Type] => Property Mappings
  • Add new Navigation Property mapping.
  • Enter the name for the new property.It should be unique.
  • For Resolver Type enter "Telerik.Sitefinity.Web.Services.Contracts.TaxonomyRelationResolver"
  • Add a parameter with key "propName" and value the name of taxonomy field (for ex. "Categories")
  • Save Changes

Now you will have your taxonomy field exposed in the OData service.
You can use $expand in the query to include it in the results, or a combination of $expand=FieldName($select=Id,Title) to get a faceted result set.

NOTE: This property is read only and you cannot use it for updating the field.