asp.net + MongoDB数据库 批量删除如何做?求高手

            public void MonogDBUpdate(Guid empId)        {            QueryDocument query = new QueryDocument();            query.Add("EmployeeId", empId);            query.Add("State", AuditState.Uncommitted);            UpdateDocument update = new UpdateDocument();            update.Add("State", AuditState.Pending);            update.Add("SubmitTime", DateTime.Now.ToLocalTime());            DatabaseHelper.Update(Tables.EmployeeLogs, query, update, UpdateFlags.Multi);                    }  public static SafeModeResult Update(string collection, IMongoQuery query, IMongoUpdate update,UpdateFlags fla)        {                        if (query == null)                throw new ArgumentNullException("参数 query 不能为null");            if (update == null)                throw new ArgumentNullException("参数 update 不能为null");            var db = DatabaseHelper.GetDataBase();            MongoCollection c = db.GetCollection(collection);            return c.Update(query, update, fla,SafeMode.False);        }