ListView not updated after adding new items to List

Question

I have a ListView bounded to a List of a class I created. When doing an operating, it was supposed to add/remove items from the list, but my ListView wasn't updated even though I used INotifyPropertyChanged.

If I use ObservableCollection, it works but I need to have the list sorted, and ObservableCollection doesn't do sorting for WPF4.0 :(

Any way I can make the List binding work? Why didn't it work even though I used INotifyPropertyChanged?

XAML:

<ListView BorderThickness="0" ItemsSource="{Binding SelectedValues, UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" Padding="5">
                    <ListView.View>
                        <GridView ColumnHeaderContainerStyle="{StaticResource myHeaderStyle}">
                            <GridViewColumn DisplayMemberBinding="{Binding Value}"></GridViewColumn>

VM:

    private List<CheckBoxItem> _selectedValues = new List<CheckBoxItem>();

    public List<CheckBoxItem> SelectedValues
            {
                get { return _selectedValues; }
                set
                {
                    _selectedValues = value;
                    OnPropertyChanged();
                }
            }

    private void UnselectValueCommandExecute(CheckBoxItem value)
            {
                value.IsSelected = false;
                SelectedValues.Remove(value);
                //OnPropertyChanged("SelectedValues");
                OnPropertyChanged("IsAllFilteredValuesSelected");
            }

public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
        }

The CheckBoxItem class contains 2 properties, Value and IsChecked, which I don't think is relevant here.

So basically, I have a button which uses the UnselectValueCommandExecute to remove items from the list, and I should see the list updated in the UI, but I'm not.

When I debug, I can see the SelectedValues list updated, but not my UI.

Answer 1

You need a CollectionViewSource in your UI.

The XAML:

<Window x:Class="WavTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    
        xmlns:scm="clr-namespace:System.ComponentModel;assembly=WindowsBase"        
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <CollectionViewSource Source="{Binding TestSource}" x:Key="cvs">
            <CollectionViewSource.SortDescriptions>
                <scm:SortDescription PropertyName="Order"/>
            </CollectionViewSource.SortDescriptions>
        </CollectionViewSource>
    </Window.Resources>
    <ListView ItemsSource="{Binding Source={StaticResource cvs}}" DisplayMemberPath="Description"/>
</Window>

The code behind:

namespace WavTest
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            var vm = new ViewModel();
            this.DataContext = vm;

            vm.TestSource.Add(new TestItem { Description="Zero", Order=0 });
        }
    }

    public class ViewModel 
    {
        public ObservableCollection<TestItem> TestSource { get; set; }

        public ViewModel()
        {
            TestSource = new ObservableCollection<TestItem>();
            TestSource.Add(new TestItem { Description = "Second", Order = 2 });
            TestSource.Add(new TestItem { Description = "Third", Order = 3 });
            TestSource.Add(new TestItem { Description = "First", Order = 1 });
        }
    }

    public class TestItem
    {
        public int Order { get; set; }
        public string Description { get; set; }
    }
}

Explanation:

The ObservableCollection raises the PropertyChanged event as you expect, but you cannot sort it. So, you need the CollectionView to sort it and bind the sorted collection to you ListView/ListBox. As you can see, adding an element after the DataContext initialization affects the UI sorting the last added item ("Zero") correctly.