Listbox always returns 0
<p>I am loading a ListBox OnSelectedChange of DropDownlist. If I select a 3rd value from the ListBox, it always returns 0. What could be wrong? I appreciate any help. Thank you. Here is my code.</p>

<pre><code>    &lt;asp:DropDownList ID="dropdown1" runat="server" Width="300" OnSelectedIndexChanged="onChange"
                                                AutoPostBack="true"&gt;
&lt;asp:ListBox ID="list1" runat="server" Width="300" Rows="12" CausesValidation="true"/&gt;


   protected void OnChange(object sender, EventArgs e)
    {
         LoadListBox();
    }

    void LoadListBox()
    {
        list1.Items.Clear();

        System.Data.DataTable rows = new System.Data.DataTable();
        rows = DAL.GetValues();
        foreach (System.Data.DataRow row1 in rows.Rows)                 {
                list1.Items.Add(new ListItem(row1["measurement"].ToString().Trim(), row1["measurement"].ToString()));
        }
     }                                               
</code></pre>
