两种实现模式，还是选择2，少一层继承。

public class Model
   {

   }


   public interface IRepository<TEntity>
   {
       /// <summary>
       /// Gets entity by key.
       /// </summary>
       /// <typeparam name="TEntity">The type of the entity.</typeparam>
       /// <param name="keyValue">The key value.</param>
       /// <returns></returns>
       TEntity GetByKey(object keyValue);
   }

   public interface IRepository
   {
       /// <summary>
       /// Gets entity by key.
       /// </summary>
       /// <typeparam name="TEntity">The type of the entity.</typeparam>
       /// <param name="keyValue">The key value.</param>
       /// <returns></returns>
       TEntity GetByKey<TEntity>(object keyValue) where TEntity : class;
   }


   public class BaseRepository   : IRepository
   {

       public TEntity GetByKey<TEntity>(object keyValue) where TEntity : class
       {
           throw new NotImplementedException();
       }
   }

   public class BaseRepository<T> : BaseRepository, IRepository<T> where T : class
   {

       public T GetByKey(object keyValue)
       {
           return this.GetByKey<T>(keyValue);
       }
   }

   public class BaseRepository2<T> : IRepository, IRepository<T> where T : class
   {

       public T GetByKey(object keyValue)
       {
           return this.GetByKey<T>(keyValue);
       }

       public TEntity GetByKey<TEntity>(object keyValue) where TEntity : class
       {
           throw new NotImplementedException();
       }
   }





   public interface IBiz
   {
       void Get();
   }

   class bbb : BaseRepository<Object>, IBiz
   {

       public void Get()
       {
           this.GetByKey(1);
           this.GetByKey<Model>(1);
       }
   }