protected void Page_Load(object sender, EventArgs e)
 {
     if (!IsPostBack)
     {
         Admin admin = (Admin)Session["admin"];
         if (admin == null)
         {
             Response.Redirect("~/Login.aspx");
         }
         else
         {
             Sql  = "select 学号=Student.StudentID,姓名=StudentName,班级=StudentClass,指导老师=teacherName,标题名=titleName from Student,teacher,title where 1=1 and STitleID=TitleID and TEID=title.TeacherID";
             Sql2 = "select 学号=Student.StudentID,姓名=StudentName,班级=StudentClass,指导老师='无',标题名='未选题' from Student where SudentState=0";
             ddlTeacher.DataSourceID = null;
             ddlTeacher.DataSource   = studentManage.GetAllClass();
             ddlTeacher.DataBind();
             ddlTeacher.Items.Insert(0, new ListItem("请选择班级", "-1"));
             DataSet dataset = studentManage.GetStudent(Sql + " union " + Sql2);
             GridView1.DataSourceID = null;
             GridView1.DataSource   = dataset;
             GridView1.DataBind();
         }
     }
 }