its help you
<asp:TemplateField HeaderText="DELETE" HeaderStyle-BackColor="#8d3736" HeaderStyle-CssClass="gridheader">
<ItemTemplate>
<asp:ImageButton ID="ImageButton8" runat="server" CommandName="del"
ImageUrl="~/Images/delete.png"
onclientclick="return confirm('Do You Want To Delete?')"
onclick="ImageButton8_Click" />
</ItemTemplate>