WPF binding with PlacementTarget and RelativeSource

wpf binding datacontext
MadSeb picture MadSeb · Feb 16, 2011 · Viewed 13.8k times · Source

Can you explain the following WPF code:

DataContext="{Binding Path=PlacementTarget,RelativeSource={x:Static RelativeSource.Self}}">

I find it extremely confusing. What is placement target and what is relative source?

Answer

HCL picture HCL · Feb 16, 2011

This looks like a hack that is used for popup-elements such as ContextMenus and Popup-windows.
The problem with these elements is, that they are disconnected from the visual tree of your window. Therefore the DataContext is not available. The PlacementTarget is a link to an element of the visual-tree.
Mostly you will find a binding binding path like PlacementTarget.Tag where in the source element the Tag property has been set to the DataContext but in some situations, the element itself is also meaningfull, such as in your example.

Assuming that the above code is used in a ToolTip or a ContextMenu, the DataContext will be set to the control that "owns" the element.

Look at the post from (Gishu +1) for an explanation of the mechanics.

Related questions

How to hide a control if the underlying DataContext is null?

I have an object in my view model that has a bunch of properties, some of them will occasionally be null. I don't want to just show some controls if these particular controls are null. How would I go about …

Read More
Use DataContext as CommandParameter in WPF

I want to pass the current DataContext (which is an instance of a ViewModel) as a CommandParameter on a WPF Button. What would be the syntax I should use? <Button x:Name="btnMain" Command="infra:ApplicationCommands.MyCommand" CommandParameter="{Binding ???}" /&…

Read More
wpf how to bind to DataContext existence?

I set the datacontext dynamically in code. I would like a button on screen to be enabled/disabled depending if DataContext == null or not. I can do it in code when I assign the DataContext but it would be better …

Read More