Question

I have an UserControl containing a ItemsSource DependenceProperty that has to be binded to the ItemsSource property of an internal Control:

ItemsSource="{Binding ItemsSource, RelativeSource={RelativeSource Self}}"

vs

ItemsSource="{Binding ItemsSource, ElementName=controlName}"

controlName is the name of the control.

The first binding is not working while the second one works. I don’t get the difference.

Any ideas?

EDIT:

XAML:

<UserControl x:Class="MultiSelectTreeView.MultiSelectableTreeView"

         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 

         mc:Ignorable="d"

         Name="multiTree" >

This does not work ---> <TreeView ItemsSource="{Binding ItemsSource, RelativeSource={RelativeSource Self}}" >
This works ---> <TreeView ItemsSource="{Binding ItemsSource, ElementName=multiTree}" >

Answer 1

In case you want to bind to DP of parent UserControl, you need to bind it using Mode = FindAncestor. Since you are binding on internal control, you need to travel up the Visual Tree.

Self Mode will search for DP in internal control and not on parent UserControl.

ItemsSource="{Binding ItemsSource, RelativeSource={RelativeSource FindAncestor, 
                                                   AncestorType=UserControl}}"