//得到选择课程的学生表,是当前学年学期的选课的学生，往年的要专门查询查Selecion表
public IList<Student> GetSelectCourseStudent(int courseId)
{
ICourseDao courseDao = new CourseDao(sessionFactory);
Course selectedCourse = courseDao.Get(courseId);
string studyYear = selectedCourse.courseStudyYear;
string term = selectedCourse.courseTerm;
ISelectionDao selectionDao = new SelectionDao(sessionFactory);
//Selection表，是否为空？否则就是NullException
IList<Selection> selectionList=selectionDao.GetSelectionByCourse(courseId,studyYear,term);
//IList<Student> studentList=null;
//(还未分配空间，一定要分配了空间给一个对象才可以用其实例方法)
IList<Student> studentList =new List<Student>();
IStudentDao studentDao = new StudentDao(sessionFactory);
for (int i = 0; i < selectionList.Count; i++) {
studentList.Add(studentDao.Get(selectionList[i].ID.selectionStudentID));
}
return studentList;
}
public Student GetStuentByID(string userId)
{
int studentId = Int32.Parse(userId);
IStudentDao studentDao = new StudentDao(sessionFactory);
return studentDao.Get(studentId);
}