/// <summary>
/// 根据单元获取题库信息
/// </summary>
/// <param name="unitid"></param>
/// <returns></returns>
public string GetQuestion(int unitid, string tp, string qn)
{
List <BackQuestionBank> list = question.GetQuestionById(unitid, tp, qn);
return(Newtonsoft.Json.JsonConvert.SerializeObject(list));
}