Collapsible panel extender

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HTML

Ajax

C#3.5

I have trawled the net over the last couple of days to find a way of solving my issue, quite a few have done it a different way to the way I've done it but I need to keep my project running the same

I'm using Visual Studio 2008, SQL Server 2008 with AJAX and C#

I've got a grid which is returning data as a cumulative total, it all works without an issue, have attached a collapsible panel extender and another grid to display sub elements, this is where I'm having difficulty as I cannot see the second gridview.

When it gets to the following I get an error "Object not set to an instance of an object"
((GridView)FindControl("GridView2)).DataSource = reader1;

Any assistance most appreciated, code below, have had to top and tail it due to content

What I have tried:

<asp:ScriptManager ID="ScriptManager1" runat="server">
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="EmplID" CellPadding="4" ForeColor="#333333" GridLines="None" Width="700px" onrowcommand="GridView1_RowCommand"
onrowediting="GridView1_RowEditing">
<rowstyle backcolor="#EFF3FB">
<columns> <asp:BoundField DataField="EmpID" HeaderText="EmpID" InsertVisible="False" ReadOnly="True" SortExpression="EmpID" Visible="False" />
<asp:TemplateField HeaderText="Project/Order" SortExpression="linknumber" HeaderStyle-HorizontalAlign="Center">
<itemtemplate>
<asp:LinkButton ID="LinkButton1" runat="server" Text='<%# Bind("EmpID") %>'>


<cc1:CollapsiblePanelExtender ID="CollapsiblePanelExtender1" runat="server"
TargetControlID="Panel1" CollapsedSize="0"
Collapsed="true" ExpandControlID="LinkButton1" CollapseControlID="LinkButton1"
AutoCollapse="false" AutoExpand="false"
ScrollContents="true" ExpandDirection="Vertical">

<asp:Panel ID="Panel1" runat="server">
<asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="False" DataKeyNames="EmpID">
<columns> <asp:TemplateField HeaderText="EmpID">
<itemtemplate>
<asp:Label ID="lblAbID" runat="server" Text='<%# Bind("AbID") %>'>

<itemstyle width="50px" horizontalalign="Center">

<asp:TemplateField HeaderText="EmpID">
<itemtemplate>
<asp:Label ID="lblEmpIDD" runat="server" Text='<%# Bind("Date","{0:dd/MM/yyyy}") %>'>

<itemstyle width="50px" horizontalalign="Center">





<HeaderStyle HorizontalAlign="Center"></HeaderStyle>

<asp:TemplateField HeaderText="EmpID">
<itemtemplate>
<asp:Label ID="lblEmpID" runat="server" Text='<%# Bind("EmpID") %>'>

<itemstyle width="50px" horizontalalign="Center">

<asp:TemplateField HeaderText="SerNo">
<itemtemplate>
<asp:Label ID="lblESerNoID" runat="server" Text='<%# Bind("SerNo") %>'>

<itemstyle width="100px" horizontalalign="Center">

C# Code
protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
try
{
SQLQueryDD = "select e.EmployeeID, e.SerNo from tbl_Emp e where e.EmpID = 12";

FullStringDD = SQLQueryDD;
SqlCommand cmd = new SqlCommand(FullStringDD, connAMP);

connAMP.Open();

GridViewRow row = (GridViewRow)(((LinkButton)e.CommandSource).NamingContainer);
reader1 = cmd.ExecuteReader();
((GridView)FindControl("GridView2")).DataSource = reader1;
((GridView)FindControl("GridView2")).DataBind();
connAMP.Close();
}
catch (Exception ex)
{

}
}