how we can get hidden field value to update records in DB

Question

hi, i am using C# ASP.net ,

i have a form where two textboxes to save and then below a grid view where display the records now i want to this hidden field value during update a table records.

<asp:TemplateField HeaderText="From">

<ItemTemplate>

<asp:Label ID="lblfromdt" runat="server" Text='<%# Eval("FromDate", "{0:MMM-yyyy}")%>'></asp:Label>

<asp:HiddenField ID="CustomerId" runat="server" Value='<%# Bind("Id") %>' />

</ItemTemplate>

<ItemStyle CssClass="textAlignCenter" />

<HeaderStyle CssClass="textAlignCenter" />

</asp:TemplateField>

 

protected void grdFY_SelectedIndexChanged(object sender, EventArgs e)

{

string FromDT = (grdFY.SelectedRow.FindControl("lblfromdt") as Label).Text;

string ToDT = (grdFY.SelectedRow.FindControl("lbltodt") as Label).Text;

txtFinancialYearFrom.Text = FromDT;

txtFinancialYearTo.Text = ToDT;

string s = ((HiddenField)grdFY.SelectedRow.Cells[0].FindControl("CustomerId")).Value;

Id = Convert.ToInt16(s);

} 

 

this Id value i want to pass on button click on same page outside of gridview.

please help me how i can