public virtual void Insert(IEnumerable<TEntity> entities)
        {
            if (entities == null)
                throw new ArgumentNullException(nameof(entities));

            try
            {
                Entities.AddRange(entities);
                _context.SaveChanges();
            }
            catch (DbUpdateException exception)
            {
                //ensure that the detailed error text is saved in the Log
                throw new Exception(GetFullErrorTextAndRollbackEntityChanges(exception), exception);
            }
        }

/// <summary>
        /// 回滚实体更改并返回完整的错误消息
        /// </summary>
        /// <param name="exception">Exception</param>
        /// <returns>Error message</returns>
        protected string GetFullErrorTextAndRollbackEntityChanges(DbUpdateException exception)
        {
            //rollback entity changes
            if (_context is DbContext dbContext)
            {
                var entries = dbContext.ChangeTracker.Entries()
                    .Where(e => e.State == EntityState.Added || e.State == EntityState.Modified).ToList();

                entries.ForEach(entry =>
                {
                    try
                    {
                        entry.State = EntityState.Unchanged;
                    }
                    catch (InvalidOperationException)
                    {
                        // ignored
                    }
                });
            }
            
            try
            {
                _context.SaveChanges();
                return exception.ToString();
            }
            catch (Exception ex)
            {
                //if after the rollback of changes the context is still not saving,
                //return the full text of the exception that occurred when saving
                return ex.ToString(); 
            }
        }