如何使用Case语句

使用C#.Net和MYSQL

我想使用像SQL这样的CASE语句

SELECT vehicleno, 
       brandname, 
       CASE 
         WHEN inexpire < 0 THEN 'Expired' 
         ELSE inexpire 
       END AS inexpire 
FROM   (SELECT Concat(plateno, vehicleno)   AS vehicleno, 
               brandname, 
               Datediff(inedate, Curdate()) AS inexpire 
        FROM   tb_car 
        WHERE  inedate < DATE_ADD(Curdate(), INTERVAL 30 DAY) 
        GROUP  BY vehicleno) AS tab1 

当我运行查询时,它将输出显示为

System.Byte[] 而不是“过期”

在上面的查询中,infire是列值