Question

if the parent’s datasource has a child property that is a collection (let’s say it is called ChildCollection) is there a trick to reference it?

So, this code sample is basically what I am attempting to do. But when I use this approach I do not get any data to my child controls.

<UserControl>
    <UserControl.Resources>
        <sample:Data x:Key="MyData" />
    </UserControl.Resources>
    <Canvas DataContext="{StaticResource MyData}">
        <TextBlock Text="{Binding Title}" />
        <My:UserControl DataContext="{Binding ChildCollection}" />
    </Canvas>
</UserControl>

My dependency property looks like this:

public static readonly DependencyProperty DataProperty =
    DependencyProperty.Register("Data", typeof(IEnumerable), typeof(ButtonList), 
    new UIPropertyMetadata(new PropertyChangedCallback(DataChanged)));
public DoubleCollection Data
{
    get { return (DoubleCollection)GetValue(DataProperty); }
    set { SetValue(DataProperty, value); }
}
static void DataChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
    (sender as FrameworkElement).DataContext = e.NewValue;
}
public void SetData(IEnumerable data)
{
    (View as CollectionViewSource).Source = data;
}

Thank you in advance for your help.

Answer 1

If I understand your code right, you want the collection to be in the UserControl’s DataProperty.

To achieve this, you have to do the Binding like this:

 <Canvas DataContext="{StaticResource MyData}">
    <TextBlock Text="{Binding Title}" />
    <My:UserControl Data="{Binding ChildCollection}" />
 </Canvas>

Instead of:

<Canvas DataContext="{StaticResource MyData}">
    <TextBlock Text="{Binding Title}" />
    <My:UserControl DataContext="{Binding ChildCollection}" />
 </Canvas>

Hope this is helpful. Also: I dont know if a canvas inherits it’s DataContext to childs. Use a Panel instead (Grid/Stackpanel/WrapPanel).

Jan