title: Can WCF contract methods return null?
body: <p>I have a fixed-sized multidimensional collection exposed via a WCF contract, and I want to be able to return null for any coordinates in the collection that have not been populated. When I try this, I get an exception indicating that this is not supported: "FaultException`1: Object reference not set to an instance of an object."</p>
  
  <p>I wondered whether some flag of OperationContract could be used, but none stand out.</p>
  
  <p>Is what I want possible, or is there some intrinsic restriction within WCF?</p>
  
  <p>Thanks</p>