public abstract class Dog
      {
         public abstract void Bark();
      }

      public interface IFeedable
      {
         void Feed();
      }

      public class Doberman : Dog , IFeedable
      {
         //Why override here
         public override void Bark()
         {
            throw new NotImplementedException();
         }

         //and not here?
         public void Feed()
         {
            throw new NotImplementedException();
         }
      }