ef core 公共接口封装

show me code:

    public interface ICommonDAL<T> where T : class, new()
    {
        protected EFContext context { get; }
        /// <summary>
        /// 新增一个实体
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public int Add(T entity)
        {
            if (entity == null)
                return -1;
            context.Entry<T>(entity).State = Microsoft.EntityFrameworkCore.EntityState.Added;
            return context.SaveChanges();
        }
        /// <summary>
        /// 批量添加
        /// </summary>
        /// <param name="entitys"></param>
        /// <returns></returns>
        public int BatchAdd(List<T> entitys)
        {
            if (entitys == null)
                return -1;
            foreach (T item in entitys)
            {
                context.Entry<T>(item).State = Microsoft.EntityFrameworkCore.EntityState.Added;
            }
            return context.SaveChanges();
        }
        public int Deleted(T entity)
        {
            if (entity == null)
                return -1;
            context.Entry<T>(entity).State = Microsoft.EntityFrameworkCore.EntityState.Deleted;
            return context.SaveChanges();
        }
        public T AddReturnEntity(T entity)
        {
            context.Entry(entity).State = Microsoft.EntityFrameworkCore.EntityState.Added;
            int count = context.SaveChanges();
            if (count > 0)
                return entity;
            else
                return null;
        }
        public int Update(T t, string keyName)
        {
            var entry = context.Entry<T>(t);
            //把user对象加入上下文,但是没有改变
            entry.State = Microsoft.EntityFrameworkCore.EntityState.Unchanged;
            //使用反射找到不为空的字段
            foreach (var item in t.GetType().GetProperties())
            {
                //虚拟属性是导航属性
                if (item.GetMethod.IsVirtual)
                {
                    continue;
                }
                //拿到属性值
                object obj = item.GetValue(t);
                if (obj != null)
                {
                    //不是主键才去修改，如果是主键就不需要修改了
                    if (item.Name != keyName)
                    {
                        //表示该字段需要更新
                        entry.Property(item.Name).IsModified = true;
                    }
                }
            }
            return context.SaveChanges();
        }
        public T GetElementById(int Id)
        {
            string name = typeof(T).Name;
            T element = context.Database.SqlQuery<T>("select * from " + name + " where Id=@Id", new SqlParameter("@Id", Id)).FirstOrDefault();
            return element;
        }
        //public T GetMyNoteFileById(int Id)
        //{
        //    T value = context.Set<T>().Where(a=>a.);
        //    return myNoteFile;
        //}
    }