GridView and Hidden Fields - asp.net

Question

I've got a Web app, in VB/ASPX, with a GridView fill with a SqlDataSource in my aspx file. Like this :
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
DataSourceID="SqlDataSource1" SkinID="dataGrid" onrowcommand="GridView1_RowCommand">
<Columns>
<asp:TemplateField AccessibleHeaderText="id_session" HeaderText="id_session">
<EditItemTemplate>
<asp:TextBox ID="txt_id_session" runat="server" Text='<%# Bind("id_session") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="lbl_id_session" runat="server" Text='<%# Bind("id_session") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:Formation_2014ConnectionString %>"
SelectCommand="SELECT s.id_session, f.libelle_formation, s.date_debut_session, s.date_fin_session, COUNT(p.id_personne) AS Expr1 FROM Sessions AS s LEFT OUTER JOIN Participe AS p ON p.id_session = s.id_session AND p.actif = 1 RIGHT OUTER JOIN Formation AS f ON f.id_formation = s.id_formation WHERE (s.date_fin_session > GETDATE()) OR (s.date_fin_session < GETDATE()) OR (S.date_fin_session = GETDATE()) GROUP BY s.id_session, f.libelle_formation, s.date_debut_session, s.date_fin_session" >
</asp:SqlDataSource>
This parts works, after that I'm hiding the first column, "id_session" with this code in my CodeBehind :
Protected Sub OnRowCreated(ByVal sender As Object, ByVal e As GridViewRowEventArgs) Handles GridView1.RowCreated
GridView1.Columns(0).Visible = False
'e.Row.Cells(0).Visible = False 'This way delete my paging
(Requête)
End Sub
And after that, I have to get the value of this Hidden column in my vb code, i'm trying different way but nothing ><
Dim id_session = GridView1.SelectedRow.Cells(0).Controls(0).ToString 'Return System.Web.UI.Literalcontrol
Dim id_session = GridView1.SelectedRow.RowIndex 'Return number of line
Sorry for my english, i'm French !

Answer 1

use the Hiddenfield
try the following code insted of useing textbox in the firest column
<asp:HiddenField ID="hf_sessionId" runat="server" Value='<%# Bind("id_session") %>' />
it will not show to the UI and you can easily access the value from it
with this code you don't need the RowCreated event of the grid
dear remove this code
<ItemTemplate>
<asp:Label ID="lbl_id_session" runat="server" Text='<%# Bind("id_session") %>'></asp:Label>
</ItemTemplate>
and put the hiddenfield into the other itemtemplate which you want to display

Answer 2

Instead of "GridView1.Columns(0).Visible = False" change your code like this,
GridView1.Columns(0).style("display")="none"

Answer 3

I finally found this method :
Dim id_session = (CType(GridView1.SelectedRow.Cells(0).Controls(1), Label)).Text
It Work !