Question

I have an ObservableCollection in the VM that is displayed in the view in a ListView. When the selected item changes, the SelectionChanged event fires nicely. Below is how I have the ListView configured:

<ListView Grid.Row="3" Margin="5" AlternationCount="2" Name="_lvSettings" 
          IsSynchronizedWithCurrentItem="True"
          ItemsSource="{Binding Path=CollectionView}" 
          SelectedIndex="{Binding Path=SelectedSettingIndex}"
          SelectionChanged="OnSelectionChanged"  >
    <ListView.View>
        <GridView>
            <GridViewColumn Width="170" 
                            Header="{Binding Path=ShowAllDisplay}"
                            x:Name="_colSettings"  
                            DisplayMemberBinding="{Binding Path=Setting}"/>
            <GridViewColumn Header="Old Value" Width="150" 
                            DisplayMemberBinding="{Binding Path=OldVal}"/>
            <GridViewColumn Header="New Value" 
                            DisplayMemberBinding="{Binding Path=NewVal}" />
        </GridView>
    </ListView.View>
</ListView>

The problem I have is when I change the filter on the collection. The selected item remains the same, which is good, but the ListView changes to display from the first item, and often the selected item is out of view (but still the selected item).

In the VM, I have the property “SelectedSettingIndex” that throws the PropertyChanged event when it changes. Even if I raise the event myself manually (base.OnPropertyChanged(“SelectedSettingIndex”);) from the VM when the filter changes, the event does not seem to really get raised as the property did not really change. There must be a way to call ScrollIntoView or something similar in this scenario, but I can’t figure out the correct event or trigger to do so. What is it that I am missing?

EDIT

Here is a, hopefully better, description of the issue I am concerned with:

1) I am using a CollectionViewSource in the VM to filter data.

2) There is a button for the user to toggle between a filter.

3) Lets assume the ListView has room to show up to 10 items at any given time.

4) The user selects item “A” in the filtered view which is at index 50 in the listview.

5) The user then clicks the button to turn filtering off.

Expected Results: The ListView is populated with the unfiltered list, Item “A” remains selected, and the ListView is “scrolled” such that item “A” is still visible.

Actual Results: The ListView is populated with the unfiltered list, Item “A” remains selected, and the ListView is “scrolled” to the top and showing the first 10 items. Item “A” is not in view.

Answer 1

Keep the SelectedItem of your ListView in a property:

public MyTypeOfObject SelectedItem { get; set; }

Assign the binding to XAML:

<ListView Name="MyListView" SelectedItem="{Binding SelectedItem}"...></ListView>

Now whenever you change filter do:

if (SelectedItem != null)
    MyListView.ScrollIntoView(SelectedItem);

EDIT:

To do it in your user control, in order to leave you view model clean from control references (ListView), catch a standard CollectionView event there or define your own that will be fired after filter or other job happened.