c# (asp.net) fasten preference values constants codebehind

aspx code

<asp:radiobuttonlist id="rbserver" runat="server" >
   <asp:listitem value=<%=serverdeveloper%>> developer </asp:listitemv
   <asp:listitem value="dev.ahsvendor.com"> dev.test.com</asp:listitem>
   <asp:listitem value="staging.ahsvendor.com"> staging.test.com</asp:listitem>
</asp:radiobuttonlist>

aspx.cs - codebehind

const twine serverdeveloper = "developer";

aspx error: formula blocks upheld context.

question: repremand proceed tie an dropdown/radio buttion/... aspx value consistent common codebehind code?

i know i rbserver.add.item("developer") [from codebehind], nonetheless there proceed grasp display side things?