Here’s my existing code:
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"
DataSourceID="dsEmployees" DataTextField="Last_First"
DataValueField="EmpNum"
onselectedindexchanged="DropDownList1_SelectedIndexChanged">
</asp:DropDownList>
Yonita, you need some more moving parts. You need a datasource to bind to, for instance.
Have a look at the Data Access tutorials on the ASP.NET website:
http://www.asp.net/learn/data-access/