Nested ItemControls - Binding to Upper Control

Question

I have got one Collection wich contains a Collection itself. Now I want to go through both Collections in wpf. I'm trying to bind the Color Property of the second Collection to a Dependency Property of the first Collection. But until now, I didn't find a way to Bind it Properly. In case of Visibility-Binding I found a work-around by binding the Visibility-Property of the canvas layout in the second ItemsPanelTemplate to the wanted property.

Here's some piece of code which represents my situation:

<ItemsControl x:Name="Itemcntrl10" ItemsSource="{Binding Collection1}" >
                    <ItemsControl.ItemsPanel>
                        <ItemsPanelTemplate>
                            <Canvas />
                        </ItemsPanelTemplate>
                    </ItemsControl.ItemsPanel>
                    <ItemsControl.ItemTemplate>
                        <DataTemplate>
                            <ItemsControl x:Name="Itemcntrl12" ItemsSource="{Binding Collection2}"  > 
                                <ItemsControl.ItemsPanel>
                                    <ItemsPanelTemplate>
                                        <Canvas Visibility="{Binding Visibility, Converter={StaticResource BooleanToVisibilityConverter}}" />
                                    </ItemsPanelTemplate>
                                </ItemsControl.ItemsPanel>
                                <ItemsControl.ItemTemplate>
                                    <DataTemplate>
                                            <Line X1="{Binding X}" Y1="{Binding Y}" 
                                                  X2="{Binding old.X}" Y2="{Binding old.Y}" 
                                                  StrokeThickness="{Binding Path=DataContext.StrokeThickness, ElementName=ThisMainWindow}" 
                                                   >
                                            <Line.Stroke>
                                                <SolidColorBrush  Color="Black" />
                                            </Line.Stroke>
                                        </Line>
                                    </DataTemplate>
                                </ItemsControl.ItemTemplate>
                            </ItemsControl>
                        </DataTemplate>
                    </ItemsControl.ItemTemplate>
                </ItemsControl>

Any ideas how to get this handled ? I thought about ElementBinding to the upper ItemsControl but this didn't solve my problem either.

Answer 1

You can use a RelativeSource binding to access an item further up the VisualTree

For example,

Color="{Binding RelativeSource={RelativeSource AncestorType={x:Type Canvas}}, 
                Path=DataContext.SomeColorProperty}"

This should look up your VisualTree for the closest Canvas object, which will be the one used in Itemcntrl12, and it will bind to it's DataContext, which should be a data item in your first ItemsControl.

If you wanted to go up another level and bind to a property of the first ItemsControl (Itemcntrl10), you could use the AncestorLevel property of the binding to specify the 2nd Canvas instead of the first one.