Dynmically create dropdownlist inside gridview

I want to create dynamic dropdownlist inside Gridview control.

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
        BackColor="White" BorderColor="#CCCCCC" BorderStyle="None" BorderWidth="1px" 
        CellPadding="4" ForeColor="Black" GridLines="Horizontal" Height="241px" 
        Width="374px">
            <Columns>
             
               
                <asp:TemplateField HeaderText="designation">
                    <ItemTemplate>
                        <asp:DropDownList ID="dd_desghnation" runat="server">
                            <asp:ListItem> --Select--</asp:ListItem>
                          
                        </asp:DropDownList>
                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
            <FooterStyle BackColor="#CCCC99" ForeColor="Black" />
            <PagerStyle BackColor="White" ForeColor="Black" HorizontalAlign="Right" />
            <SelectedRowStyle BackColor="#CC3333" Font-Bold="True" ForeColor="White" />
            <HeaderStyle BackColor="#333333" Font-Bold="True" ForeColor="White" />
        </asp:GridView>

Something like this...I don't know how can I do that....

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