Question

How can I append this

<% =i %>

variable onto this.

<asp:DropDownList ID="AdTitle" runat="server">

Cant have this for some reason.

<asp:DropDownList ID="AdTitle<% =i %>" runat="server">

Answer 1

You shouldn’t need to dynamically generate ids in this way.

Use a repeater (or any other repeating control with item templates):

<asp:Repeater ID="forEachItem" runat="server">
    <ItemTemplate>
        <asp:DropDownList ID="AdTitle" runat="server" />
        <%!-- any other content per item --%>
    </ItemTemplate>
</asp:Repeater>

Or generate your controls server side:

<asp:PlaceHolder ID="ph" runat="server" />

<%
    //...
    ph.Controls.Add( new DropDownList { Id = "AdTitle" + i } );
    //...
%>

If you use the repeater make sure you use databindings (<%#) rather than literals (<%=).