use this in GridView:
<asp:GridView ID="GrdView_Name" runat="server" AllowPaging="true" PageSize="10" PagerSettings-Mode="Numeric" OnPageIndexChanging="GrdView_Name_PageIndexChanging"...........
protected void GrdView_Name_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
GrdView_Name.PageIndex = e.NewPageIndex;
}