Replace DropDownList Text with Value on SelectedIndexChanged in ASP.Net

dear fellas,

i want to create a drop down list, where user can view the code name and the name the code when they click on the drop down list.

but after they choose, only the code is appeared.

this is my current coding as for now. 

<asp:DropDownList ID="ddlcodetype" runat="server">
                                          <asp:ListItem Selected="True">-</asp:ListItem>
                                          <asp:ListItem>DK Deck</asp:ListItem>
                                          <asp:ListItem>EG Engine</asp:ListItem>
                                          <asp:ListItem>CT Catering</asp:ListItem>
                                          <asp:ListItem>OT Others</asp:ListItem>
                                      </asp:DropDownList>

with this, both my name and the code name are appeared. 

can anyone tell me how i should this?