WPF Binding to parent ItemsControl from inside of child ItemsControl data template

Question

I need to be able to bind to a parent ItemsControl 's properties from inside of a child ItemsContro l data template:

<ItemsControl ItemsSource="{Binding Path=MyParentCollection, UpdateSourceTrigger=PropertyChanged}">
    <ItemsControl.ItemTemplate>
        <DataTemplate>

                <ItemsControl ItemsSource="{Binding Path=MySubCollection}">
                    <ItemsControl.ItemTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding Path=MyParentCollection.Value, UpdateSourceTrigger=PropertyChanged}"/>
                        </DataTemplate>
                    </ItemsControl.ItemTemplate>
                </ItemsControl>

        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

Let's assume that MyParentCollection (the outer collection) is of the following type:

public class MyObject
{
    public String Value { get; set; }
    public List<MyChildObject> MySubCollection { get; set;
}

And let's assume that MyChildObject from the above class is of the following type:

public class MyChildObject
{
    public String Name { get; set; }
}

How can I bind to MyParentCollection.Value from inside of the inner data template? I can't really use a FindAncestor by type because they both all levels use the same types. I thought maybe I could put a name on the outer collection and use an ElementName tag in the inner binding, but that still couldn't resolve the property.

Any thoughts?

Answer 1

saving the parent item in the tag of the child itemscontrol could work

    <DataTemplate>

            <ItemsControl ItemsSource="{Binding Path=MySubCollection}" Tag="{Binding .}">
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding Path=Tag.Value, RelativeSource={RelativeSource  AncestorType={x:Type ItemsControl}}}"/>
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>

    </DataTemplate>

its not tested but give you a hint in the right direction :)

Answer 2

Binding for Tag , as suggested in the other answer, is not required. All data can be obtained from DataContext of ItemControl (and this markup Tag="{Binding}" just copies DataContext into Tag property, which is redundant).

<ItemsControl ItemsSource="{Binding Path=MyParentCollection}">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <ItemsControl ItemsSource="{Binding Path=MySubCollection}">
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding Path=DataContext.Value, RelativeSource={RelativeSource AncestorType=ItemsControl}}"/>
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>