private void bntOK_Click(object sender, EventArgs e)
 {
     ClassQuestionMark.BLL.StudentBLL bstudent = new StudentBLL();
     if (stuinfo != null)
     {
         stuinfo.LabClassID = cmbClass.ClassID;
         if (bstudent.UpdateStudent(stuinfo))
         {
             MessageBox.Show(stuinfo.SName + "��ת��" + stuinfo.LabClassID + "�࣡");
             return;
         }
     }
        MessageBox.Show("ת��ʧ�ܣ�");
 }