up is a method to set it's OnSelectedIndexChanged as index_changed to reflect SelectedIndexChaged event,certainly you can write in code-behind like:
private void drop_SelectedIndexChanged(object sender, System.EventArgs e)
{
lbl.Text=drop.SelectedItem.Text;
}
it's SelectedIndexChanged. and you should set dropdownlist's AutoPostBack property as true.
forexample:
<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
<html>
<script language="C#" runat="server">
ICollection CreateDataSource() {
DataTable dt = new DataTable();
DataRow dr;