Child item in TreeView not updating

Question

I copied the basic method of having checkbox in a treeview from the official Silverlight toolkit Checkboxes in a TreeView example.

When a user clicks on a parent TreeViewItem I want all of the child items to be checked, as in the above example. This works fine when the parent is collapsed, clicking the checkbox puts a tick in the parent and when you expand the node all children have a tick in the checkbox.

However it doesn't work if the parent is expanded. None of the children are updated to have a tick in the checkbox, although the underlying data list is updated.

My XAML is as follows:

<sdk:HierarchicalDataTemplate x:Key="NodeTemplate" ItemsSource="{Binding Path=Contracts}">
    <StackPanel Orientation="Horizontal" ToolTipService.ToolTip="{Binding Path=Name}">
        <CheckBox IsTabStop="False" IsThreeState="{Binding Path=HasContracts}" IsChecked="{Binding Path=Selected, Mode=TwoWay}" Click="CheckBox_Click" />
        <TextBlock Text="{Binding Path=Name}" Tag="{Binding Path=ID}"/>
    </StackPanel>
</sdk:HierarchicalDataTemplate>

    <sdk:TreeView x:Name="tvClientContract" ItemsSource="{Binding Path=ClientContracts, Mode=TwoWay}" ItemTemplate="{StaticResource NodeTemplate}"/>

This is bound to a List<ClientContract> and uses the same code behind as in the linked example.

The ClientContract object is:

public int ID { get; set; }
public string Name { get; set; }
public List<ClientContract> Contracts { get; set; }
public bool? Selected { get; set; }

How can I force the child to repaint itself as the underlying List<ClientContract> object is updated?

Answer 1

Try using ObservableCollection<ClientContract> instead of a List<>. Usually you want to databind to this collection type instead when the data is dynamic so it can notify the UI of collection changes.

Answer 2

If you want to use INotifyPropertyChange(what I did instead of using ObservableCollection) here is how you do it per example on the ID element:

public class myclass : INotifyPropertyChanged
{
    private int id_Value;
    public int ID
    {
        get { return id_Value; }
        set
        {
            id_Value = value;
            NotifyPropertyChanged("ID");
        }
    }

    public string Name { get; set; }
    public List<ClientContract> Contracts { get; set; }
    public bool? Selected { get; set; }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(string name)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(name));
    }
}

I hope this helps if it was what you were trying to do.