error

Question

 protected void Page_Load(object sender, EventArgs e)
        {
            classfill();
        }
        public void classfill()
        {
            ClassSp spclass = new ClassSp();
            DataTable dtblclass = new DataTable();
            dtblclass = spclass.classViewAll();
            ddlclasname.DataSource = dtblclass;
            ddlclasname.DataValueField = "classId";
            ddlclasname.DataTextField = "className";
            ddlclasname.DataBind();
            ddlclasname.Items.Insert(0, "--select--");

            

        }
        public void divfill()
        {
            DivisionSp spdivision = new DivisionSp();
            DataTable dtblc = new DataTable();
            dtblc = spdivision.divisionSearch(DivSearch);
            ddldivisionname.DataSource = dtblc;
            ddldivisionname.DataValueField = "divisionId";
            ddldivisionname.DataTextField = "divisionName";
            ddldivisionname.DataBind();
            ddldivisionname.Items.Insert(0, "--select--");


        }
then


 protected void ddlclasname_SelectedIndexChanged(object sender, EventArgs e)
        {
            DivSearch = ddlclasname.SelectedValue.ToString();
            divfill();
        }

but div is not fill