Export to excel selected records from gridView

Question

Hello,

 

I have a new functionality that I have to add to my ASP.NET solution and I could use some help. 

What I need to do is to select some records from a gridview  (based on select checkbox) and export those records to an excel file.

Here's my gridView:

     <asp:GridView ID="gv" runat="server" AutoGenerateColumns="false" ShowFooter="true"
      OnPageIndexChanging="gv_PageIndexChanging" AllowPaging="True" PageSize="20">
    <Columns>
        <asp:TemplateField HeaderText="S/N" ItemStyle-Width="25">
            <ItemTemplate>
                <asp:Label ID="lblrownum" runat="server"  Text='<%#Eval("rownum") %>' Width="25"></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Appno">
            <ItemTemplate>
                <asp:Label ID="lblAppNo" runat="server" Text='<%#Eval("Appno") %>' Width="40"></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="IDNO">
            <ItemTemplate>
                <asp:Label ID="lblIDNO" runat="server" Text='<%#Eval("IDNO") %>' Width="40"></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Select" >
            <ItemTemplate>
                <asp:CheckBox ID="cbSelected" runat="server" />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
      <PagerStyle HorizontalAlign="Left" VerticalAlign="Middle"/>
</asp:GridView>

<asp:Button ID="btnExport" runat="server" Text="Export to Excel" />

Any kind of help would be appreciated.

 

Thank you in advnce.