Remove additional vertical whitespace from WPF

<Border CornerRadius="2,2,2,2" BorderThickness="1" BorderBrush="LightSkyBlue" Margin="5,2,2,2" x:Name="PersonBorder" Visibility="Collapsed"><StackPanel Orientation="Vertical"><ListBox Name="personListBoxTest"          BorderThickness="0"          ScrollViewer.HorizontalScrollBarVisibility="Hidden"          ScrollViewer.VerticalScrollBarVisibility="Auto"          HorizontalContentAlignment="Stretch"          Background="LemonChiffon"><ListBox.ItemTemplate ><DataTemplate><StackPanel><StackPanel Orientation="Horizontal" Background="Pink"><StackPanel Orientation="Horizontal" Visibility="{Binding ElementName=Involvement, Path=Text, Converter={StaticResource cIsVisibleOrCollapsed}}" Margin="0,0,5,0"><TextBlock Text="Involvement:"/><TextBlock Margin="5,0,0,0" Text="{Binding Path=NameInvolvementType}" Foreground="Blue" x:Name="Involvement"/></StackPanel><StackPanel Orientation="Horizontal"><TextBlock  Text="Name:"/><TextBlock Margin="3,0,0,0" Text="{Binding Path=FirstName}" Foreground="Blue" /><TextBlock Margin="3,0,0,0" Text="{Binding Path=MiddleName}" Foreground="Blue" /><TextBlock Margin="3,0,0,0" Text="{Binding Path=LastName}" Foreground="Blue" /><TextBlock Margin="3,0,0,0" Text="{Binding Path=NameSuffix}" Foreground="Blue" /><TextBlock Margin="5,0,0,0" Text="DOB:"/><TextBlock Margin="3,0,0,0" Text="{Binding Path=BirthDate, StringFormat=MM/dd/yyyy}" Foreground="Blue" /></StackPanel></StackPanel><StackPanel  Visibility="{Binding ElementName=myEventAddress,Path=Visibility, Converter={StaticResource cVisibilityMirror}}" Orientation="Horizontal"><TextBlock Text="Address:" /><EventDet:EventAddress Margin="5,0,0,0" x:Name="myEventAddress" Foreground="Blue" CityTextBlockOrientation="Horizontal" /></StackPanel><StackPanel Visibility="{Binding ElementName=Phone1, Path=Text, Converter={StaticResource cIsVisibleOrCollapsed}}" Orientation="Horizontal"><TextBlock Text="Home:" /><TextBlock Margin="5,0,0,0" Text="{Binding Path=Phone1}" Foreground="Blue" x:Name="Phone1"/></StackPanel><StackPanel Visibility="{Binding ElementName=Phone2, Path=Text, Converter={StaticResource cIsVisibleOrCollapsed}}" Orientation="Horizontal"><TextBlock Text="Mobile:" /><TextBlock Margin="5,0,0,0" Text="{Binding Path=Phone2}" Foreground="Blue" x:Name="Phone2"/></StackPanel><StackPanel Visibility="{Binding ElementName=Phone3, Path=Text, Converter={StaticResource cIsVisibleOrCollapsed}}" Orientation="Horizontal"><TextBlock Text="Work:" /><TextBlock Margin="5,0,0,0" Text="{Binding Path=Phone3}" Foreground="Blue" x:Name="Phone3"/></StackPanel><StackPanel x:Name="PersonAlertSP" Visibility="Collapsed" Background="WhiteSmoke"><TextBlock Text="Alerts:" /><ListBox ItemsSource="{Binding Path=PersonAlertList}" x:Name="PersonAlertListBox"  BorderThickness="1"><ListBox.ItemTemplate><DataTemplate><StackPanel Orientation="Horizontal"><TextBlock Text="{Binding Path=AlertType}" Margin="0,0,5,0" Foreground="Blue" Width="150"/><TextBlock Text="{Binding Path=Description}" Margin="0,0,5,0" Foreground="Blue"/></StackPanel></DataTemplate></ListBox.ItemTemplate></ListBox></StackPanel></StackPanel></DataTemplate></ListBox.ItemTemplate></ListBox></StackPanel></Border>

code behind:

//this is a little unweidly, but its test code until this worksMobileWPF.singleton.EventDetailsTabControl.myEventDetailControl.personListBoxTest.ItemsSource =    dc.SessionEvent.SessionPersons.ToList();

Here's an image of the result with 6 items, all the data is nonsense test data:

EDIT 2:

After playing around with it a bit, I guess this is what's happening... First the ListBox is greedy and takes the maximum amount of vertical space, then some IValueConverter computations are done, and some elements are collapsed. However, once this is done, the ListBox height is not being updated.

EDIT 3:

I tried converting PersonListBoxTest into an ItemsControl, instead of a ListBox, with teh only difference in code being that and the <ItemsControl.ItemTemplate > declaration... And now it works as expected, no extra whitespace.

So somehow the ItemsControl respects the fact that some of my elements are collapsed through the IValueConverters, and the ListBox doesn't. I played around with the VirtualizingStackPanel attribute in ListBox, setting IsVirtualizing to both true and false (no change), before testing the ItemsControl.

I'll give the points to anyone who can explain why it works how I observed it.
Thanks for your answers everyone, you never know what's going to make the difference.

Here's an example of an IValueConverter, which is being used, they are all about the same.

[ValueConversion(typeof(object), typeof(System.Windows.Visibility))]public class NullToVisibleOrCollapsed : IValueConverter{    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)    {        if (value == null) return System.Windows.Visibility.Collapsed;        if (value is Image)        {            if (((Image)value).Source == null) return System.Windows.Visibility.Collapsed;            return System.Windows.Visibility.Visible;        }        if (value is string)        {            string myString = (string)value;            if (string.IsNullOrEmpty(myString) == true)                return System.Windows.Visibility.Collapsed;        }        if (value is int)        {            int myInt = (int)value;            if (myInt == 0)                return System.Windows.Visibility.Collapsed;        }        return System.Windows.Visibility.Visible;    }