Binding “BindingList” to DataTemplate with converter does not update

Question

I have view model BindingList<Wave> .

here is the model (only one property is shown).

public class Wave : INotifyPropertyChanged
{
    private double _period;

    public double Period
    {
        get { return _period; }
        set
        {
            if (value.Equals(_period)) return;
            _period = value;
            OnPropertyChanged(nameof(Period));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

Below Im trying to bind view model into canvas and draw them with polyline which works but only once.

The problem is that when i change the properties the view does not update. (the converter does not fire after first time).

<ItemsControl ItemsSource="{Binding WaveCollection, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:MainWindow}}}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <Canvas />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Polyline Points="{Binding Converter={StaticResource PlotterConverter}}"/>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

PlotterConverter just returns PointCollection . with some formula but its not important here.

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    return new PointCollection(GetPoints(value as Wave));
}

Answer 1

您没有使用Binding Mode = TwoWay 。

<Polyline Points="{Binding ., Mode=TwoWay, Converter={StaticResource PlotterConverter}}"/>