CODEWITHSUNDEEP
wpfsilverlightdata-bindingbinding
Alexander Boriskin
Alexander Boriskin

Reputation: 155

RelativeSource and Popup

The problem is that RelativeSource does not work in the following case. I use silverlight 5.

//From MainPage.xaml
<Grid x:Name="LayoutRoot" Background="White" Height="100" Width="200">
    <Popup IsOpen="True">
        <TextBlock Text="{Binding Path=DataContext, RelativeSource={RelativeSource AncestorType=Grid}}" />
    </Popup>
</Grid>

//From MainPage.xaml.cs
public MainPage()
{
    InitializeComponent();
    DataContext = "ololo";
}

If I set a breakpoint on the binding, I'll get Error:

System.Exception: BindingExpression_CannotFindAncestor.

If I use ElementName=LayoutRoot instead of RelativeSource, everything will be OK.

Why does the relative source binding not work?

Upvotes: 9

Views: 6756

Answers (4)

17 of 26
17 of 26

Reputation: 27382

As others have mentioned, it's because the Popup is not part of the visual tree. Instead, you can use the Popup's PlacementTarget property to get back to the visual tree:

<Grid x:Name="LayoutRoot" Background="White" Height="100" Width="200">
    <Popup IsOpen="True">
        <TextBlock Text="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Popup}}, 
                                  Path=PlacementTarget.DataContext}" />
    </Popup>
</Grid>

Upvotes: 2

Rover
Rover

Reputation: 2230

You can make small hack: setup DataContext via resources.

<Grid.Resources>
    <Style TargetType="TextBlock">
        <Setter Property="DataContext" Value="{Binding ElementName=myGrid, Path=DataContext}" />
    </Style>
</Grid.Resources>

Upvotes: 2

yo chauhan
yo chauhan

Reputation: 12305

Popup is like ContextMenu , ToolTip controls , They are not added to the VisualTree. For this you will have to do like

<Grid x:Name="LayoutRoot" Height="100" Width="200" Background="Black">
    <Popup Grid.Row="0"  x:Name="popup" DataContext="{Binding PlacementTarget.DataContext, RelativeSource={RelativeSource Mode=Self}}">
        <TextBlock Text="{Binding DataContext, ElementName=popup}" Background="Red" Width="30" Height="30" />
    </Popup>
</Grid>

public MainWindow()
    {
        InitializeComponent();
        DataContext = "abcd";
        popup.PlacementTarget = LayoutRoot; 
    }

I hope this will help.Not like in case of ContextMenu or Tooltip , here you will also have to specify the PlacementTarget.

Upvotes: 10

user2055119
user2055119

Reputation: 19

Popups are not part of the visual tree.

Relative Source "Gets or sets the binding source by specifying its location relative to the position of the binding target (MSDN)". Since Popups are not part of the visual tree of the control that is showing it, it will not be able to resolve anything outside of the popup.

Upvotes: 0

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