WCF ria服务返回复杂类型的列表

我有一个复杂类型的实体

public class ComplexEntity : ComplexObject
{
private int _ID;
private string _Name;
private int _ParentID;
[Key]
[DataMember]
public int ID { get;set;}
[DataMember]
public string Name {get;set;}
[DataMember]
public int ParentID {get;set;}
}

和另一个

[DataContract]
public class ComplexEntitiesList : ComplexObject
{
[DataMember]
[Include]
[Association("CEntities_CEntity","ID","ParentID")]
public List<CompelxEntity> List {get;set;}
[Key]
[DataMember]
public int ID {get;set;}
public int LKEntitiesList()
{
List = new List<LKEntity>;
}

和方法:

[Invoke]
public ComplexEntitiesList GetPS()
{
return new ComplexEntitiesList() { List = /*..some logic*/});
}

在服务器端，一切都是完美的，但在客户端，列表是空的有线索吗?}

[Invoke]
public IEnumerable<ComplexEntity> GetPS() {
  return new List<ComplexEntity>() { /*..some logic*/});
}