Question

I have made a CheckedListBox using the following:

<ListBox x:Name="lst_checkBoxList" ItemsSource="{Binding}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <CheckBox Content="{Binding Name}" IsChecked="{Binding IsChecked}" />
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

and am populating it using the following:

public List<CheckedListItem> listItems = new List<CheckedListItem>();

public class CheckedListItem
{
    public int Id { get; set; }
    public string Name { get; set; }
    public bool IsChecked { get; set; }

    public CheckedListItem(int id, string name, bool ischecked)
    {
        Id = id;
        Name = name;
        IsChecked = ischecked;
    }
}

private void button1_Click(object sender, RoutedEventArgs e)
{
    listItems.Add(new CheckedListItem(0, "item 1", false));
    listItems.Add(new CheckedListItem(0, "item 2", false));
    listItems.Add(new CheckedListItem(0, "item 3", false));
    listItems.Add(new CheckedListItem(0, "item 4", false));
    lst_checkBoxList.ItemsSource = listItems;
    listItems[0].IsChecked = true; //This correctly sets the first CheckBox as checked.
}

private void button2_Click(object sender, RoutedEventArgs e)
{
    listItems[0].IsChecked = true; //This does not affect the CheckBox, despite changing the value it is bound to.
}

If I change the data behind one of the CheckBoxes immediately after setting the ItemsSource, the CheckBox is ticked accordingly, but if I try to change the value anywhere else in the code the CheckBox remains unchecked…can anyone help me work out why?

Answer 1

You need to notify the control that the property it is bound to has been updated, by implementing the INotifyPropertyChanged interface in CheckedListItem:

public class CheckedListItem : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private bool _IsChecked;
    public bool IsChecked 
    { 
        get { return _IsChecked; }
        set 
        {
            _IsChecked = value;
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs("IsChecked"));
        }
    }
}