IF在标记中阻止更改数据源

Question

我在test.aspx文件中有以下代码：

<% If (Session("username") <> "lok.dmt") Then%>
    <asp:dropdownlist id="id_loket"
        DataSource="<%# ModuleName.DefaultView %>"
        DataTextField="name_modul"
        DataValueField="id_modul"
        Width="385"
        runat="server"> </asp:dropdownlist>
<% Else%>             
    <asp:dropdownlist id="id_loket"
        DataSource="<%# ModuleNameDMT.DefaultView %>"
        DataTextField="name_modul"
        DataValueField="id_modul"
        Width="385"
        runat="server"> </asp:dropdownlist>           
<% End If%>   

当我运行该文件时，我收到以下错误;

Parser Error Message: The ID 'id_loket' is already used by another control.