RepositoryAdd.cs

public class Repository<TEntity> : IReporitory<TEntity> where TEntity : class
{
      protected readonly DbContext Context;
      protected readonly DbSet<TEntity> Entities;

      public Repository(DbContext context)
      {
          Context = context;
          Entities = Context.Set<TEntity>();
      }

      public void Add(TEntity entity)
      {
          Entities.Add(entity);
      }
}