I have the following classes as models:

attachment 1 is the profile class. 2 is the Measrements class and 3 is the web api.

The return profile object contains a measurement list with 4 objects. When I execute the call to the rest api:

localhost/30504/api/Setting/1, I get the following error in attachment 4:

When I remove the list object from profile, it works just fine. How do I get this to serialize/deserialize correctly?
Thanks in advance for you help... I'm new at this..