Cannot serialize parameter of type 'System.Linq.Enumerable… ' when using WCF, LINQ, JSON

Question

I have a WCF Service. It uses Linq-to-objects to select from a Dictionary. The object type is simple:

public class User 
{
   public Guid Id;
   public Stri         


        

Answer 1

No, one must return a concrete class from a web service. Make the return type List and be done with it.