When I use code with generic:
    var parenttable = MobileService.GetTable<TParent>();
    var testid = await parenttable.Where(prnt => prnt.Id == 20).ToListAsync();
where TParent: IEnity
public interface IEnity
{
    int Id { get; set; }
}
I catch the exception:
The member 'Id' is not supported in the 'Where' Mobile Services query expression 'Convert(prnt).Id'.
But if I change the generic to type:
   var parenttable = MobileService.GetTable<Category>();
   var testid = await parenttable.Where(prnt => prnt.Id == 20).ToListAsync();
I have normal result. Why? And how can I use generic?