Someone

<%@ Page Language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            DropDownList1.Items.Add("A");
            DropDownList1.Items.Add("B");
            DropDownList1.Items.Add("C");
            DropDownList1.Items.Add("D");
        }
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True">
        </asp:DropDownList>
    </div>
    </form>
</body>
</html>