Nested gridview not showing data inside updatepanel , its shows undefined - asp.net

Question

Data not showing in nested gridview.I have tried and googled but not
getting solution. Nested gridview is placed inside the updatepanel,
collapsible works fine but data not showing in the gvCandidate grid.
It showing undefined.
<asp:UpdatePanel ID="MainUpdatePanel" runat="server">
> <ContentTemplate>
> <asp:GridView ID="gvdlgEditTestScores" runat="server" CssClass="gvdlgEditTestScores"
>
> ShowFooter="false" ShowHeader="true" EnableViewState="True" GridLines="None"
> EmptyDataText="No records found" AutoGenerateColumns="false" CaptionAlign="Left" CellPadding="0"
> CellSpacing="0" ShowHeaderWhenEmpty="True"
> OnRowDataBound="gvdlgEditTestScores_RowDataBound"> <Columns>
> <asp:TemplateField ItemStyle-CssClass="" HeaderStyle-CssClass="" HeaderText="TestScore">
> <ItemTemplate>
> <asp:TextBox ID="gvdlgEditTestScores_Vocab" runat="server" Text='<%# Eval("Vocab") %>' ReadOnly="true"></asp:TextBox>
> </ItemTemplate>
> </asp:TemplateField>
> <asp:Panel ID="pnlCandidate" runat="server" Style="display: none;">
> <asp:GridView ID="gvCandidate" runat="server" EnableViewState="True" GridLines="None"
> EmptyDataText="No records found" AutoGenerateColumns="false" CaptionAlign="Left"
> CssClass="gvCandidateAssignedHistory">
> <Columns>
> <asp:BoundField ItemStyle-Width="100px" DataField="OrderId" HeaderText="Order Id" />
> <asp:BoundField ItemStyle-Width="100px" DataField="OrderAmount" HeaderText="Amount" />
> </Columns>
> </asp:GridView>
> </asp:
Data not showing in nested gridview.I have tried and googled but not getting solution.
Nested gridview is placed inside the updatepanel, collapsible works fine but data not showing in the gvCandidate grid. It showing undefined.
>
<asp:UpdatePanel ID="MainUpdatePanel" runat="server">
> <ContentTemplate>
> <asp:GridView ID="gvdlgEditTestScores" runat="server" CssClass="gvdlgEditTestScores"
>
> ShowFooter="false" ShowHeader="true" EnableViewState="True" GridLines="None"
> EmptyDataText="No records found" AutoGenerateColumns="false" CaptionAlign="Left" CellPadding="0"
> CellSpacing="0" ShowHeaderWhenEmpty="True"
> OnRowDataBound="gvdlgEditTestScores_RowDataBound"> <Columns>
> <asp:TemplateField ItemStyle-CssClass="" HeaderStyle-CssClass="" HeaderText="TestScore">
> <ItemTemplate>
> <asp:TextBox ID="gvdlgEditTestScores_Vocab" runat="server" Text='<%# Eval("Vocab") %>' ReadOnly="true"></asp:TextBox>
> </ItemTemplate>
> </asp:TemplateField>
> <asp:Panel ID="pnlCandidate" runat="server" Style="display: none;">
> <asp:GridView ID="gvCandidate" runat="server" EnableViewState="True" GridLines="None"
> EmptyDataText="No records found" AutoGenerateColumns="false" CaptionAlign="Left"
> CssClass="gvCandidateAssignedHistory">
> <Columns>
> <asp:BoundField ItemStyle-Width="100px" DataField="OrderId" HeaderText="Order Id" />
> <asp:BoundField ItemStyle-Width="100px" DataField="OrderAmount" HeaderText="Amount" />
> </Columns>
> </asp:GridView>
> </asp:Panel> </Columns>
> </ContentTemplate>
> </asp:UpdatePanel>
<script type="text/javascript">
> function pageLoad(sender, args) {
> $(document).ready(function () {
> //NESTED GRID EXPAND
> $("[src*=plus]").one("click", plus);
> });
> }
> function plus() {
> $(this).closest("tr").after("<tr><td></td><td></td><td colspan='50' style='padding-left:2%;'>" + $(this).next().html() +
> "</td></tr>");
> $(this).attr("src", "images/main/minus.png");
> $(this).one("click", minus);
> }
> function minus() {
> $(this).attr("src", "images/main/plus.png");
> $(this).closest("tr").next().remove();
> $(this).one("click", plus);
> } </script>
>
> protected void gvDashboardTestScores_RowDataBound(object sender, GridViewRowEventArgs e)
> {
> DataTable dttable = new DataTable();
>
> dttable.Columns.Add(new DataColumn("OrderId", typeof(string)));
> dttable.Columns.Add(new DataColumn("OrderAmount", typeof(string)));
>
> DataRow dtrow = dttable.NewRow();
> dtrow[0]="100";
> dtrow[1]="150";
>
> dttable.Rows.Add(dtrow);
>
> GridView gvCandidateAssignedHistory = (GridView)e.Row.FindControl("gvCandidateAssignedHistory");
> gvCandidateAssignedHistory.DataSource = dttable;
> gvCandidateAssignedHistory.DataBind();
>
> }
Panel>
> </Columns>
> </ContentTemplate>
> </asp:UpdatePanel>
<script type="text/javascript">
> function pageLoad(sender, args) {
> $(document).ready(function () {
> //NESTED GRID EXPAND
> $("[src*=plus]").one("click", plus);
> });
> }
> function plus() {
> $(this).closest("tr").after("<tr><td></td><td></td><td colspan='50' style='padding-left:2%;'>" + $(this).next().html() +
> "</td></tr>");
> $(this).attr("src", "images/main/minus.png");
> $(this).one("click", minus);
> }
> function minus() {
> $(this).attr("src", "images/main/plus.png");
> $(this).closest("tr").next().remove();
> $(this).one("click", plus);
> } </script>
>
> protected void gvDashboardTestScores_RowDataBound(object sender, GridViewRowEventArgs e)
> {
> DataTable dttable = new DataTable();
>
> dttable.Columns.Add(new DataColumn("OrderId", typeof(string)));
> dttable.Columns.Add(new DataColumn("OrderAmount", typeof(string)));
>
> DataRow dtrow = dttable.NewRow();
> dtrow[0]="100";
> dtrow[1]="150";
>
> dttable.Rows.Add(dtrow);
>
> GridView gvCandidateAssignedHistory = (GridView)e.Row.FindControl("gvCandidateAssignedHistory");
> gvCandidateAssignedHistory.DataSource = dttable;
> gvCandidateAssignedHistory.DataBind();
>
> }
Data not showing in nested gridview.I have tried and googled but not
getting solution. Nested gridview is placed inside the updatepanel,
collapsible works fine but data not showing in the gvCandidate grid.
It showing undefined.
see this Gridview image