C# - Silverlight Ria Domain Service Not Being Called While Making?

Im using silverlight ria services and trying to called a domain service method. the domain service class signature goes like this public class UserDomainService : DomainService and I have a simple operation to return data

public IQueryable GetUsers()
{
return userService.GetAll()
).AsQueryable();
}

this compiles fine an a silverlight proxy is generated on the silverlight client side. how ever when makeing calls from silverlight eg

LoadOperation op = UserDomainContext.Load(UserDomainContext.GetUsers(),UserLoadedCallback,null);
int i = op.Entities.Count();

it is always 0, the domain servcice method is never hit when i put a breakpoint.