How can I bind to a parent UIElement within an ItemTemplate? - wpf

Question

I'm trying to bind to a property of MainWindow, but from a ContextMenu within a DataTemplate. How can I achieve this?
I can't use ElementName, as the contextMenu isn't part of the visual tree
I can't use PlacementTarget, as this will give the UIElement produced by the DataTemplate
<Window x:Class="WpfApplication24.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ItemsControl ItemsSource="{Binding Data}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border Padding="5" CornerRadius="10" BorderThickness="1" BorderBrush="Red">
<Border.ContextMenu>
<ContextMenu ItemsSource="{Binding <I want to bind to a property of MainWindow here>}"/>
</Border.ContextMenu>
<TextBlock Text="{Binding}"/>
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>

Answer 1

You can have the window object in Tag of your Border and then can access it using PlacementTarget.Tag
<DataTemplate>
<Border Padding="5" CornerRadius="10" BorderThickness="1" BorderBrush="Red"
Tag="{Binding RelativeSource={RelativeSource FindAncestor,
AncestorType=Window}}">
<Border.ContextMenu>
<ContextMenu ItemsSource="{Binding PlacementTarget.Tag.PropertyName,
RelativeSource={RelativeSource Self}}"/>
</Border.ContextMenu>
<TextBlock Text="{Binding}"/>
</Border>
</DataTemplate>

Answer 2

What I used is a simple custom control wrapper e.g. MyContextMenu
...with just one line of code, something like...
public class MyContextMenu : ContextMenu
{
public override void EndInit()
{
base.EndInit();
NameScope.SetNameScope(this, NameScope.GetNameScope(App.Current.MainWindow));
}
}
...and use that instead of ContextMenu.
That always 'scopes' to the MainWindow which may not always be optimal - but you can use ElementName etc.
2) The other option is using NameScope.NameScope="{StaticResource myNameScope}"
NameScope.NameScope seems like an optimal solution - however, you cannot bind from it (and it binds 'too late').
But you can use {StaticResource ...} - and you make a class which wraps around MainWindow's scope.
Similar, but I found the above 'less disruptive' (you can pretty much write the code you'd normally write).
For more details take a look at this answers (and for more ideas)...
ElementName Binding from MenuItem in ContextMenu
How to access a control from a ContextMenu menuitem via the visual tree?