public virtual void Update(T entity)
 {
     using (RentaCarContext context = new RentaCarContext())
     {
         var deleteEntity = context.Entry(entity);
         deleteEntity.State = EntityState.Deleted;
         context.SaveChanges();
     }
 }
 public virtual void Add(T entity)
 {
     using (RentaCarContext context = new RentaCarContext())
     {
         var addedEntity = context.Entry(entity);
         addedEntity.State = EntityState.Added;
         context.SaveChanges();
     }
 }