asp:listbox loosing value on auto postback - asp.net

Question

I have an asp list box that is populated from the code behind
<asp:ListBox ID="UploadsApprovedCountries" EnableViewState="true" runat="server" Rows="1" AutoPostBack="True" OnSelectedIndexChanged="SelectedCountryChange"></asp:ListBox>
protected void Load_Countries()
{
ListItem ps = new ListItem("Please select", "");
ps.Value = "";
UploadsApprovedCountries.Items.Add(ps);
foreach (string cntry in Countries.CountriesArray())
{
UploadsApprovedCountries.Items.Add(new ListItem(cntry, cntry));
}
}
and in my Page_Load I call it like this
if (!IsPostBack)
{
Load_Countries();
}
and on autopostback calls this method
protected void SelectedCountryChange(object sender, EventArgs e)
{
filter = UploadsApprovedCountries.SelectedItem.Value;
Response.Write("line 589");
}
However nothing I seem to do ever actually calls this method. The filter string is never populated and "Line 589" is never wrote out.
Can anyone help out
the whole of my asp.net page
asp:Content ContentPlaceHolderID="ContentMainBody" ID="LocalMainBody" runat="server">
<h1> administration</h1>
<div class="clearboth"></div>
<div>
<div class="demo">
<div id="tabs">
<ul>
<li>Uploads awaiting approval</li>
<li>Uploads approved</li>
<li>Sign-ups awaiting approval</li>
<li>Sign-ups approved</li>
<li>Rejected</li>
</ul>
<div id="tabs-5">
<h2>Rejected submissions</h2>
<div id="rejectedSubmissions" runat="server">
</div>
</div>
<div id="tabs-1">
<h2>Uploads awaiting approval</h2>
<div id="matUnautherised" runat="server">
</div>
<div class="clearboth"></div>
</div>
<div id="tabs-3">
<h2>Uploads live on site</h2>
<asp:ListBox ID="UploadsApprovedCountries" EnableViewState="true" runat="server" Rows="1" AutoPostBack="True" OnSelectedIndexChanged="SelectedCountryChange" OnTextChanged="SelectedCountryChange"></asp:ListBox>
<div id="matAutherised" runat="server">
</div>
<div class="clearboth"></div>
</div>
<div id="tabs-2">
<h2>Sign-ups awaiting approval</h2>
<div id="signups" runat="server">
</div>
<div class="clearboth"></div>
</div>
<div id="tabs-4">
<h2>Sign-ups live on site</h2>
<div id="signupsapproved" runat="server">
</div>
</div>
</div>
</div>
</div>
I have just noticed that if I change my code in my listbox to this
<asp:ListBox ID="UploadsApprovedCountries" EnableViewState="true" runat="server" Rows="1" AutoPostBack="True" OnSelectedIndexChanged="SelectedCountryChange">
<asp:ListItem Value="test1" Text="test1"></asp:ListItem>
<asp:ListItem Value="test2" Text="test2"></asp:ListItem>
<asp:ListItem Value="test3" Text="test3"></asp:ListItem>
<asp:ListItem Value="test4" Text="test4"></asp:ListItem>
<asp:ListItem Value="test5" Text="test5"></asp:ListItem>
</asp:ListBox>
and don't populate it from the data source then it works as it should. Is there a difference between adding the items from the code behind and adding them directly like above?

Answer 1

simple really once you know how
protected override void OnInit(EventArgs e)
{
base.OnInit(e);
Load_Countries();
UploadsApprovedCountries.EnableViewState = true;
}