I want to hide columns in asp.net in GridView then access the values in GridViewSelectIndexChanged using vb.net. I am using hidden fields in the GridView. When I try to access gives me an error object reference not set to an instance here is the code
<asp:GridView ID="GridView1" runat="server" OnSorting="GridView1_OnSorting" AllowPaging="True" AllowSorting="True"
AutoGenerateColumns="False"
BorderStyle="Outset" CellPadding="4" DataSourceID="odsA02_Tracking"
ForeColor="#333333" GridLines="Vertical" Style="border-right: #0000ff thin solid;
table-layout: auto; border-top: #0000ff thin solid; font-size: x-small; border-left: #0000ff thin solid;
border-bottom: #0000ff thin solid; font-family: Arial; border-collapse: separate" Font-Size="Small" PageSize="30">
<FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="
White" />
<RowStyle BackColor="#EFF3FB" />
<EditRowStyle BackColor="#2461BF" />
<SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
<PagerStyle BackColor="#2461BF" ForeColor="
White" HorizontalAlign="Center" />
<HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="
White" />
<AlternatingRowStyle BackColor="
White" />
<Columns>
<asp:CommandField ShowSelectButton="True" />
<asp:boundfield datafield="Since" HeaderText="Submit Date" ReadOnly=true SortExpression="Since" />
<asp:BoundField DataField="Started_By" HeaderText="Submitted By" SortExpression="Started_By" />
<asp:BoundField DataField="Client_FullName" HeaderText="Client Name" ReadOnly="True" SortExpression="Client_FullName" />
<asp:BoundField DataField="Product_Desc" HeaderText="Product" ReadOnly="True" SortExpression="Product_Desc" />
<asp:BoundField DataField="Branch_List" HeaderText="Branch" ReadOnly="True" SortExpression="Branch_List" />
<asp:BoundField DataField="Event_AssignedID" HeaderText="Assigned To" ReadOnly="True"
SortExpression="Event_AssignedID" />
<asp:BoundField DataField="DaysElapsed" HeaderText="Days Open" ReadOnly="True" SortExpression="DaysElapsed" />
<asp:BoundField DataField="Status" HeaderText="Status" SortExpression="Status" />
<asp:TemplateField HeaderText=Instance_ID >
<ItemTemplate>
<asp:HiddenField ID=lblInstanceID Value='<%#Eval("Instance_ID") %>' runat=server>
</asp:HiddenField>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText=Seq_ID>
<ItemTemplate>
<asp:HiddenField ID=lblSeqID Value='<%#Eval("Seq_ID") %>' runat=server/>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText=Form_Code>
<ItemTemplate>
<asp:HiddenField ID=lblFormCode Value='<%#Eval("Form_Code") %>' runat=server/>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
Protected Sub GridView1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles GridView1.SelectedIndexChanged
Dim Instance_ID As String
Dim Seq_ID As String
Dim Form_Code As String
Dim PARMS As String
Dim DestinationURL As String
Dim DestinationParms As String
Dim instanceID As String = CType(GridView1.FindControl("lblInstanceID"), HiddenField).Value
End sub
