Json数据操作......[分不多了]

Oracle数据库中有表如下表名:classTable
a      b      c数学  上午   理地理  下午   理历史  下午   文政治  上午   文在C#中,取得表中内容,并将其转为Json格式字符串..
通过SQL语句: select * from classTable,然后利用OracleDataAdapter得到DataTable,利用DataTable转Json方法,会得到如下字符串:
[{"a":"数学","b":"上午","c":"理"},{"a":"地理","b":"下午","c":"理"},{"a":"历史","b":"下午","c":"文"},[{"a":"政治","b":"上午","c":"文"}]现在想根据c的值加一层进行文理分类,加标识字段d,得到如下Json字符串:
[{"c":"理","d":[{"a":"数学","b":"上午"},{"a":"地理","b":"下午"}]},{"c":"文","d":[{"a":"历史","b":"下午"},{"a":"政治","b":"上午"}]}]   请问,,如何操作比较方便,,,望哪位兄弟给出示例代码......