If you are forced to use an Anemic domain model, where do you put your business logic and calculated fields?

Question

Our current O/RM tool does not really allow for rich domain models, so we are forced to utilize anemic (DTO) entities everywhere. This has worked fine, but I continue to st

Answer 1

If your ORM technology only handles DTO objects well, that doesn't mean you have to throw out rich entity objects. You can still wrap your DTO objects with entity objects:

public class MonkeyData
{
   public string Name { get; set; }
   public List FavoriteFood { get; set; }
}

public interface IMonkeyRepository
{
   Monkey GetMonkey(string name) // fetches DTO, uses entity constructor
   void SaveMonkey(Monkey monkey) // uses entity GetData(), stores DTO
}


public class Monkey
{
   private readonly MonkeyData monkeyData;

   public Monkey(MonkeyData monkeyData)
   {
      this.monkeyData = monkeyData;
   }

   public Name { get { return this.monkeyData.Name; } }

   public bool IsYummy(Food food)
   {
      return this.monkeyData.FavoriteFood.Contains(food);
   }

   public MonkeyData GetData()
   {
      // CLONE the DTO here to avoid giving write access to the
      // entity innards without business rule enforcement
      return CloneData(this.monkeyData);
   }

}