Event in asp.net list box

<form id="form1" runat="server">
       <asp:ListBox id="ListBox1"
            OnSelectedIndexChanged="ListBox1_SelectedIndexChanged"
            AutoPostBack="true"
            runat="server">
         <asp:ListItem>Item 1</asp:ListItem>
         <asp:ListItem>Item 2</asp:ListItem>
         <asp:ListItem>Item 3</asp:ListItem>
         <asp:ListItem>Item 4</asp:ListItem>
         <asp:ListItem>Item 5</asp:ListItem>
         <asp:ListItem>Item 6</asp:ListItem>
       </asp:ListBox>

       <asp:Label id="Label1" runat="server"/>
    </form>

protected void  ListBox1_SelectedIndexChanged(object sender, EventArgs e) 
{
    Label1.Text = "You selected " + ListBox1.SelectedItem.Text +
                     " with a value of $" + ListBox1.SelectedItem.Value +
                     ".";
   // Selection of Item4 gives: "You selected Item 4 with a value of $Item 4."
}