在mysql语法中声明变量并使用dapper查询,get exception

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
            set @i = 0;
            select @i := @i+1 as Row,Target,StartDate,EndDate
            from (
                     select target,
                            StartDate,
                            EndDate
                     from t_xxx_table
                     where 1 = 1
                       and target= @TargetSn
                     order by StartDate desc
                 )
            COMMIT;

和C代码:

using (var connection = new MySqlConnection(ConnectionString))
        {
            try
            {
                var result = connection.Query<XXXClass>(sqlString, new
                {
                    TargetSn
                });
                return result;
            }
            catch (Exception e)
            {
                throw new Exception(e.ToString());
            }
        }

获取异常“对象引用未设置为对象实例。” 我试图在连接字符串中添加'Allow User Variables=True',但没有成功。 当我移除“@I”时,可能是工作。

我想,问题在于一代又一代的人不能处理“@i”和“@TargetSn”。。

有什么解决办法吗?