protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        //Set total item count 100
        ListBox1.TotalItemCount = 100;
        
        //But only add 10 items into the ListBox
        for (int i = 0; i < 10; i++)
        {
            EO.Web.ListBoxItem item = new EO.Web.ListBoxItem("item");
            ListBox1.Items.Add(item);
        }
    }
}

Protected Sub Page_Load(sender As Object, e As EventArgs)
    If Not Page.IsPostBack Then
        'Set total item count 100
        ListBox1.TotalItemCount = 100

        'But only add 10 items into the ListBox
        For i As Integer = 0 To 9
            Dim item As New EO.Web.ListBoxItem("item")
            ListBox1.Items.Add(item)
        Next
    End If
End Sub