Hi.
It's working fine in i use the following in Gridview.
<asp:BoundField DataField="City" HeaderText="City" ItemStyle-Width="100px" />
But i found that there is no data displayed in excel file if i use the following in Gridview:
<asp:TemplateField HeaderText="Pin Code">
    <ItemTemplate>
        <asp:Label ID="lbl_pin_code" runat="server" Text='<%# Bind("pin_code") %>'></asp:Label>
    </ItemTemplate>
    <HeaderStyle HorizontalAlign="Left" />
    <ItemStyle HorizontalAlign="Left" />
</asp:TemplateField>