try something like<%@ Import Namespace="System.IO" %>
<form runat="server">
<asp:DropDownList id="DropDownList1" runat="server"/>
</form><script language="C#" runat="server">
void Page_Load(Object sender, EventArgs e)
{
  if (!IsPostBack)
  {
DirectoryInfo dri = new DirectoryInfo(Server.MapPath("."));

FileInfo[] filist = dri.GetFiles("*.aspx");
DropDownList1.DataSource = filist;
DropDownList1.DataTextField = "Name";
DropDownList1.DataValueField = "Name";
DropDownList1.DataBind();

DropDownList1.Attributes["onchange"]="javascript:window.location.href=this.value;";
string s="<script language='javascript'>function window.onload() {document.all('DropDownList1').selectedIndex=-1;}</" + "script>";
RegisterStartupScript("Startup",s);
  }
}
</script>