Thanks a lot for your reply.
I tried what you are saying but unfortunately that is not working.
I hope I am doing it correctly. To make sure that, sharing few more information.
I am hitting one of the public services. http://services.odata.org/Northwind/Northwind.svc/$metadata
I am getting edmmodel in following way:
IEdmModel edmmodel = messageReader.ReadMetadataDocument();
edmmodel.GetAnnotationValue((IEdmElement)edmmodel.SchemaElements.First(), "http://schemas.microsoft.com/ado/2009/02/edm/annotation", "StoreGeneratedPattern");
Above thing gives me null.