Detecting Selected Items (Layers) in a List Box via MVVM does not work properly

Amadeus111

I am trying to read selected items in a Listbox if selected, and a layer is created. I would like to do it with MVVM. My code does not work properly.  It selects no more than 11 items, yet creates 12 layers out of it. I am puzzled. I would appreciate any help. I am using 3.0 but I get the same result with 2.9

UPDATE:

I just noticed even though all items selected in the list box. They are not detected unless the scroll is all the way down. Selected items are detected according to the scroll position. I don't know why it acts like that.

XAML:

 

 

<ListBox x:Name="DataListBox" SelectionMode="Extended" HorizontalAlignment="Left" Margin="5,5,0,0" Grid.Row="1"  Grid.Column="0" Grid.RowSpan="8" 
                                 VerticalAlignment="Top" Height="200" Width="200"                                 
                                 ItemsSource="{Binding DataListBoxItemsSource, UpdateSourceTrigger=PropertyChanged}"
                                 SelectedItem="{Binding DataListBoxSelectedItem, UpdateSourceTrigger=PropertyChanged}"
                                >

                            <ListBox.InputBindings>
                                <KeyBinding Command="ApplicationCommands.SelectAll" Modifiers="Ctrl" Key="A" />
                            </ListBox.InputBindings>

                            <ListBox.ItemContainerStyle>
                                <Style TargetType="ListBoxItem">
                                    <Setter Property="IsSelected" Value="{Binding IsSelected}"/>
                                </Style>
                            </ListBox.ItemContainerStyle>

                            <i:Interaction.Triggers>
                                <i:EventTrigger EventName="SelectionChanged" >
                                    <i:CallMethodAction TargetObject="{Binding}" MethodName="DataListBox_SelectionChanged"/>
                                </i:EventTrigger>
                            </i:Interaction.Triggers>
                        </ListBox>

 

 

 

 

 

 

 

View Model

 

 public async void CreateLayersTOC()
        {
            if (MapView.Active != null)
            {
                if (DataListBoxSelectedItem != null || FavoriteTabsSelectedItem != null)
                    MainStackPanelIsEnabled = false;
                LayerNames = new List<string>();
                await Task.Run(() =>
                {
                    MessageBox.Show("source count " +DataListBoxItemsSource.Count); //78 and All items selected in the UI
                    if (DataListBoxSelectedItem != null)
                        foreach (ItemPresenter itemP in DataListBoxItemsSource)
                        {
                            if (itemP.IsSelected)
                            {
                                if (LayerNames.Contains(itemP.ToString()) == false)
                                    LayerNames.Add(itemP.ToString());
                            }

                        }

                    if (FavoriteTabsSelectedItem != null)
                    {
                        foreach (ItemPresenter itemP in FavListBoxItemsSource)
                        {
                            if (itemP.IsSelected)
                            {
                                if (LayerNames.Contains(itemP.ToString()) == false)
                                    LayerNames.Add(itemP.ToString());
                            }
                        }
                    }

                    MessageBox.Show("Coll" + LayerNames.Count); // Only 11 ??
                });

                foreach (KeyValuePair<string, List<string>> kvp in LayerDict)
                {
                    if (LayerNames.Contains(kvp.Value[2]))
                    {
                        await QueuedTask.Run(() =>
                        {
                            Uri layerURI = new Uri(System.IO.Path.Combine(kvp.Value[4], kvp.Value[5] + ".lyr"));
                            MapView mapView = MapView.Active;
                            Map activeMap = mapView.Map;
                            Layer mapLayer = LayerFactory.Instance.CreateLayer(layerURI, activeMap, 0, kvp.Value[2]);
                            //MainStackPanelIsEnabled = true;
                        });
                    }

                    //LayerNames.Remove(kvp.Value[2]);
                }
            }
            else
                MessageBox.Show("Make sure to have a map available before adding layers to a map");
            MainStackPanelIsEnabled = true;
        }

 

 

 

 

public class ItemPresenter : INotifyPropertyChanged
        {
            public event PropertyChangedEventHandler PropertyChanged;
            protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
            {
                this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
            }

            private readonly string _value;

            public ItemPresenter(string value)
            {
                _value = value;
            }

            public override string ToString()
            {
                return _value;
            }

            private bool _isSelected;

            public bool IsSelected
            {
                get { return _isSelected; }
                set
                {
                    if (_isSelected != value)
                    {
                        _isSelected = value;
                        OnPropertyChanged();
                    }
                }
            }
        }

 

 

 

 

 

Wolf

Ok, got it ... the screenshot helps.   So the problem is that you do a 'select all' and only items in the visible range of the listbox are selected?   I think that's a newly introduced bug in WPF (or maybe an 'optimization').

I would suggest two possible solutions:

Try the following in your listbox definition:

<ListBox VirtualizingStackPanel.IsVirtualizing="False" ... />

Or when you 'select' all items loop manually through the list and set 'IsSelected' for each item in the list.

Let me know if this doesn't work and i enhance my test app to duplicate the issue.