如何解决 标准表达式中数据类型不匹配 的问题，谢谢大家!

以下代码在执行时出现“标准表达式中数据类型不匹配。”的错误提示，请大家帮忙解惑，谢谢!

注： 2.0 + Access

        public static decimal GetLeiJiYiWuFuWuShiJian(string YiGongID,string MyYear)//返回义工年度服务总时数
        {
            DBAccess db = new DBAccess();
            string Min_Date = MyYear + "-1-1";
            string Max_Date = MyYear + "-12-31";
            string MySql = "select sum(YiWuFuWuShiShu) from [YiWuFuWuJiLu] where [YiGongID]=" + YiGongID
                         + " and ([YiWuFuWuShiJian] >='" + DateTime.Parse(Min_Date) + "'"
                         + " and [YiWuFuWuShiJian] <='" + DateTime.Parse(Max_Date) + "')";
            return (decimal)db.ExecuteScalar(MySql);
        }
错误提示如下图：

ACCESS 数据表 YiWuFuWuJiLu 如下图：