in my .aspx page
<asp:DropDownList id="DropDownList1" runat="server" AutoPostBack="True">
	<asp:ListItem Text="Senior thesis" Value="1" />
	<asp:ListItem Text="Independent study" Value="2" />
</asp:DropDownList>

in my code behind
Private Sub DropDownList1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
       Response.Write("Hello word<br>")
End Sub