WPF - property change notification from UserControl

Question

I have two UserControls (uc1 and uc2) loading into a third UserControl (shell). Shell has two properties, uc1 and uc2, of type UserControl1 and UserControl2, and each have a DependencyProperty registered to their own classes called IsDirty:

public static readonly DependencyProperty IsDirtyProperty = DependencyProperty.Register("IsDirty", typeof (bool), typeof (UserControl1));
public bool IsDirty
{
    get { return (bool) GetValue(IsDirtyProperty); }
    set { SetValue(IsDirtyProperty, value); }
}

(same code for UserControl2)

Shell has TextBlocks bound to the IsDirty properties:

<TextBlock Text="{Binding ElementName=shell, Path=Uc1.IsDirty}"/>
<TextBlock Text="{Binding ElementName=shell, Path=Uc2.IsDirty}"/>

When I change the values of IsDirty in uc1 and uc2, Shell never gets notified. What am I missing? UserControl is descendant of DependencyObject...

The same behavior occurs if I have regular properties notifying changes via INotifyPropertyChanged.

If I raise a routed event from uc1 and uc2, bubbling up to Shell, then I can catch the Dirty value and everything works, but I shouldn't have to do that, should I?

Thanks

Edit: The answer is to raise property changed event on the Uc1 and Uc2 properties or make them DPs.

Answer 1

I tried reproducing your problem using a simple setup, and it works fine for me. I'm not sure though if this setup is correct enough to replicate your situation. Anyway, I'm posting it just in case. It might be helpful:

XAML:

<Window x:Class="WpfApplication2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication2"
        x:Name="shell"
        Title="MainWindow" Height="350" Width="525">
    <StackPanel>
        <Button Click="Button_Click">Click</Button>
        <TextBlock Text="{Binding ElementName=shell, Path=Uc1.IsDirty}"/>
    </StackPanel>
</Window>

Code-Behind:

namespace WpfApplication2
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private MyUserControl uc1 = new MyUserControl();
        public MyUserControl Uc1
        {
            get { return this.uc1; }
        }

        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            this.uc1.IsDirty = !this.uc1.IsDirty;
        }


    }

    public partial class MyUserControl : UserControl
    {
        public MyUserControl()
        {
        }

        public bool IsDirty
        {
            get { return (bool)GetValue(IsDirtyProperty); }
            set { SetValue(IsDirtyProperty, value); }
        }

        // Using a DependencyProperty as the backing store for IsDirty.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty IsDirtyProperty =
            DependencyProperty.Register("IsDirty", typeof(bool), typeof(UserControl), new UIPropertyMetadata(false));

    }
}

Answer 2

Karmicpuppet's answer works well. However it didn't solve my problem because Shell is also of type UserControl. For it to work I needed to raise the property changed on Uc1 and Uc2. When I declared them as DependencyProperties all worked as expected. Duh!