asp.net网站控制并发方式问题

double count = 40;//扣除的金额

            DataTable table = SqlHelp.ExecTable("", "select * from UserInfo WHERE Price>" + count, SqlType.Sql);

            if (table.Rows.Count > 0)

            {

                double price = Convert.ToDouble(table.Rows[0]["Price"]);

                double temp = price - count;

                SqlHelp.ExecNonQuery("", "UPDATE UserInfo SET Price=" + temp + " WHERE Price=" + price + " AND Price>" + count, SqlType.Sql);

                Console.WriteLine("当前时间：" + DateTime.Now.ToString("HH:mm ss-fffffff") + "，剩余金额：" + temp);

            }