http://www.nuget.org/packages/OfferingSolutions.DataShaper/
Allows your Api to shape your data before sending it to the client.
I made this demo-solution to show how this stuff works.
Simply start the webapplication and use Fiddler or any tool you want to create http-calls and type things like
/api/Test?fields=Id,Date
or
/api/Test?fields=Id,Date,ChildClasses.Description,ChildClasses.Id
and you will get the shaped result.