How to retain scroll position when disable scrolling

In my win phone 7 app I want to disable vertical scrolling in a listbox. But when I use

listbox.SetValue(ScrollViewer.VerticalScrollBarVisibilityProperty, ScrollBarVisibility.Disabled);

The listbox scrolls to the top. How can I retain the scroll position while have scrolling disabled?

Edit: I'm thinking of disabling scrolling by swallowing events before listbox handle them. But when I tried to handle ManipulationStarted and ManipulationCompleted, I have exception. What events I should handle to make listbox cannot scroll? When I mark ManipulationStarted, ManipulationDelta and ManipulationCompleted as handled in my code, I have Null Exception with this stack trace:

at Microsoft.Phone.Gestures.GestureHelper.ReleaseMouseCaptureAtGestureOrigin()
        at Microsoft.Phone.Gestures.GestureHelper.NotifyMove(InputDeltaArgs args)
        at Microsoft.Phone.Gestures.ManipulationGestureHelper.Target_ManipulationDelta(Object sender, ManipulationDeltaEventArgs e)
        at System.Windows.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args)
        at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, String eventName)
        at Microsoft.Xna.Framework.Input.UnsafeNativeMethods.CallWindowProc(IntPtr lpPrevWndFunc, IntPtr hWnd, UInt32 msg, IntPtr wParam, IntPtr lParam)
        at Microsoft.Xna.Framework.Input.SafeNativeMethods.CallWindowProc(IntPtr lpPrevWndFunc, IntPtr hWnd, UInt32 msg, IntPtr wParam, IntPtr lParam)
        at Microsoft.Xna.Framework.Input.WindowMessageHooker.Hook.WndProc(IntPtr msgWnd, UInt32 msg, IntPtr wParam, IntPtr lParam)

Edit: I have found that default listbox works as I want when disable scrolling. But my listbox has a custom template with a stack holding ItemPresenter to disable UI virtualization. In that scenario when disable scrolling, the listbox auto scrolls to the top.

Edit: here is the listbox's template:

<phone:PhoneApplicationPage.Resources>
        <Style x:Key="ListBoxStyle1" TargetType="ListBox">
            <Setter Property="Background" Value="Transparent"/>
            <Setter Property="Foreground" Value="{StaticResource PhoneForegroundBrush}"/>
            <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Disabled"/>
            <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
            <Setter Property="BorderThickness" Value="0"/>
            <Setter Property="BorderBrush" Value="Transparent"/>
            <Setter Property="Padding" Value="0"/>
            <Setter Prope开发者_如何学编程rty="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="ListBox">
                        <ScrollViewer x:Name="ScrollViewer" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Foreground="{TemplateBinding Foreground}" Padding="{TemplateBinding Padding}">
                            <StackPanel Orientation="Vertical" Width="468">
                                <ItemsPresenter d:LayoutOverrides="Width"/>
                            </StackPanel>
                        </ScrollViewer>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </phone:PhoneApplicationPage.Resources>

and xaml:

<ListBox x:Name="MainListBox" Margin="0,0,-12,0" ItemsSource="{Binding Items}" SelectionChanged="MainListBox_SelectionChanged" Style="{StaticResource ListBoxStyle1}" GotFocus="gotfocus" LostFocus="lostfocus">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                      <StackPanel Margin="0,0,0,17" Width="432">
                          <TextBlock Text="{Binding LineOne}" TextWrapping="Wrap" Style="{StaticResource PhoneTextExtraLargeStyle}"/>
                          <TextBlock Text="{Binding LineTwo}" TextWrapping="Wrap" Margin="12,-6,12,0" Style="{StaticResource PhoneTextSubtleStyle}"/>
                      </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>

In gotfocus and lostfocus function, I disable and enable scrolling respectively. This listbox is from the default databound application. When I scroll down and click one item, the listbox scrolls to the top. It doesn't happen when I don't use a stack to hold ItemPresenter.

You can do this:

ScrollViewer.SetVerticalScrollBarVisibility(listbox, ScrollBarVisibility.Disabled);

Can't you otherwise set the property IsHitTestVisible to false to disable the scrolling?

I have a small project I'm working on, also with a custom templated listbox. I tested the following code and that seemed to work fine for me:

ScrollViewer.SetVerticalScrollBarVisibility(YourListBox, ScrollBarVisibility.Disabled);
YourListBox.ScrollIntoView(YourListBox.SelectedItem);