try this
<asp:gridview id="grdOrder" runat="server" autogeneratecolumns="False" allowpaging="True" onpageindexchanging="grdOrder_PageIndexChanging ">
</asp:GridView>
protected void grdOrder_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
try
{
grdOrder.PageIndex = e.NewPageIndex;
grdOrder.DataSource =
grdOrder.DataBind();
}
catch (Exception ex)
{
throw ex;
}
}