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 ItemsControl 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?

Can't you use FindAncestor mode, and specify both a Type and Ancestor level? — Willem van Rumpt
– Willem van Rumpt, Commented Jun 19, 2013 at 9:03
hmmm, didn't even think of ancestor level...I'll take a look at that — Robert Petz
– Robert Petz, Commented Jun 19, 2013 at 9:15

blindmeis · Accepted Answer · 2013-06-19 09:10:06Z

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 :)

Hack of the day, but nevertheless saved the day. Thank you very much! I hope that tagging binding simply makes a reference to the binding context and doesn't duplicate what's in the context.

ASh · Accepted Answer · 2019-09-06 08:34:56Z

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>

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