Forms Data Controls :: When Click On The Next Button To View Page The Gridview Disappears?

I have a small problem I am returning some data from a query and have allowed paging, however when I click on the next button to view the following page the gridview disappears.

My datasource is specified in the code behind:

<asp:Panel ID="dtpanel" runat="server" Visible="False">
<asp:GridView ID="grddetails" runat="server" AutoGenerateColumns="False" AllowPaging="True"
OnPageIndexChanging="grddetails_SelectedIndexChanged" ViewStateMode="Enabled"
onselectedindexchanged="grddetails_SelectedIndexChanged" AllowSorting="True" >
<Columns>
<asp:BoundField DataField="Col1" HeaderText="Col1" SortExpression="Col1" />
<asp:BoundField DataField="Col2" HeaderText="Col2" SortExpression="Col2" />
<asp:BoundField DataField="Col3" HeaderText="Col3" SortExpression="Col3" />
<asp:BoundField DataField="Col4" HeaderText="Col4" SortExpression="Col4" />
<asp:BoundField DataField="Col5" HeaderText="Col5" SortExpression="Col5" />
<asp:BoundField DataField="Col6" HeaderText="Col6" SortExpression="Col6" />
</Columns>
</asp:GridView>
</asp:Panel>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data;
using System.Data.SqlClient;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void GridView2_SelectedIndexChanged(object sender, GridViewCommandEventArgs e)
{
int y = Convert.ToInt32(e.CommandArgument);
Control control = GridView2.Rows[y].Cells[0].Controls[0];
LinkButton btn = control as LinkButton;
string qval = btn.Text;
string query = "SELECT * FROM Table WHERE Col LIKE '%" + qval + "%'";
string connectionString = @"Data Source=servername;Initial Catalog=dbname;Integrated Security=True";
SqlConnection accessConnection = new SqlConnection(connectionString);
SqlCommand accessCommand = new SqlCommand(query, accessConnection);
SqlDataAdapter grddetailsDataAdapter = new SqlDataAdapter(accessCommand);
DataTable grddetailsDataTable = new DataTable("Table");
grddetailsDataAdapter.Fill(grddetailsDataTable);
int dataTableRowCount = grddetailsDataTable.Rows.Count;
if (dataTableRowCount > 0)
{
grddetails.DataSource = grddetailsDataTable;
grddetails.DataBind();
}
dtpanel.Visible = true;
}
protected void GridView1_SelectedIndexChanged(object sender, GridViewCommandEventArgs e)
{
int w = Convert.ToInt32(e.CommandArgument);
Control control = GridView1.Rows[w].Cells[0].Controls[0];
LinkButton btn = control as LinkButton;
string qval2 = btn.Text;
Label1.Text = btn.Text; string query = "SELECT * FROM Table WHERE Col LIKE '%" + qval2 + "%'";
string connectionString = @"Data Source=servername;Initial Catalog=dbname;Integrated Security=True";
SqlConnection accessConnection = new SqlConnection(connectionString);
SqlCommand accessCommand = new SqlCommand(query, accessConnection);
SqlDataAdapter grddetailsDataAdapter = new SqlDataAdapter(accessCommand);
DataTable grddetailsDataTable = new DataTable("Table");
grddetailsDataAdapter.Fill(grddetailsDataTable);
grddetails.DataSource = grddetailsDataTable;
grddetails.DataBind();
dtpanel.Visible = true;
}
protected void grddetails_SelectedIndexChanged(object sender, GridViewPageEventArgs e)
{
DataTable dataTable = grddetails.DataSource as DataTable;
grddetails.PageIndex = e.NewPageIndex;
grddetails.DataBind();
dtpanel.Visible = true;
}
}