WCF with Entity Framework Error

Question

Error: The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.

I am trying to create a WCF service with Entity Framework (VS 2010, .NET 4). When I run it, I get the above error.

I read something about editing the T4 template, but it appears that it already has

[DataContractAttribute(IsReference=true)]
public partial class Person : EntityObject

and

   [DataMemberAttribute()]
        public global::System.Int32 ID
        {
            get
            {
                return _ID;
            }

I am not sure what the difference is between

[DataMemberAttribute()] and [DataMember] 

or

[DataContractAttribute(IsReference=true)] and [DataContract] 

either.

 public Person GetPersonByID(int id)
        {
            using (var ctx = new MyEntities())
            {
                return (from p in ctx.Person
                        where  p.ID == id
                        select p).FirstOrDefault();
            }
        }

How does WCF and EF work together, properly?

Answer 1

Do you have navigation properties in your Person class? Did you disable lazy loading? Otherwise it will probably try to load content for navigation properties during serialization and it fails because of closed context.

To your other questions:

[DataMemberAttribute()] and [DataMember] are same. It is just shorter name.

[DataContractAttribute(IsReference=true)] and [DataContract] are not same. IsRefrence allows tracking circular references in navigation properties. Without this parameter circular reference causes never ending recursion.