Title pretty much explains it all, its the last thing I'm trying to work into our project. We are structured with a Service Library which contains a function like so.

        /// <summary>
        /// Returns a single category based on the specified ID.
        /// </summary>
        public Category GetCategory(int CategoryID)
        {
            var RetVal = _session.Single<Category>(x => x.ID == CategoryID);
            return RetVal;
        }

Now Category is a Entity (We are using Entity Framework) we need to convert that to a CategoryViewModel.

Now, how would people structure this? Would you make sure the service function returned a CategoryViewModel? Have the controller pull the data from the service then call another function to covnert to a view model?