Hi Vijay,
Have you solved the problem already? If I understand your question correctly, you are directly returning the results from the LINQ query. However, WCF should be able to serialize these objects. Instead of returning the results directly, you should return objects of another type adorned with the DataContract attribute. This tells WCF to use the DataContractSerializer to serialize any instance of that type.
As an example, if you have an Employee class, then you should create another class like the one below:
[DataContract]
public class EmployeeData
{
[DataMember]
public int Id { get; set; }
}
After getting the results from the LINQ query, create an EmployeeData for each result, which you will then use as the return value of the WCF service operation.