ElementName Binding is failing

Question

I have the following XAML:

<Grid>
    <Grid.RowDefinitions>
        ...
    </Grid.RowDefinitions>
    <DataGrid Grid.Row="0" ...>
        <DataGrid.Columns>
            ...
        </DataGrid.Columns>
    </DataGrid>

    <DockPanel Grid.Row="2">
        <CheckBox x:Name="DisplayMarkers" DockPanel.Dock="Top" Content="Display Data Points?"
                Margin="8,5,0,5" d:LayoutOverrides="Height" HorizontalAlignment="Left" IsChecked="False" />
        <vf:Chart DockPanel.Dock="Top" ScrollingEnabled="False" ZoomingEnabled="True" ToolBarEnabled="True">
            <vf:DataSeries AxisYType="Secondary" RenderAs="Line" DataSource="{Binding CdTeRoughnessList}"
                    XValueType="DateTime"
                    MarkerEnabled="{Binding ElementName=DisplayMarkers, Path=IsChecked}" Color="Navy"
                    LegendText="Roughness Std. Dev.">

This binding is failing: MarkerEnabled="{Binding ElementName=DisplayMarkers, Path=IsChecked}"

I'm trying to bind to the IsChecked property on my Checkbox named 'DisplayMarkers". When I run this, in debug mode in VS 2010, the output window shows the binding is failing. It can't find the element named 'Checkbox'. Could anyone tell me why?

The error I'm getting from VS is:

System.Windows.Data Error: 4 : Cannot find source for binding with reference 

    'ElementName=DisplayMarkers'. BindingExpression:Path=IsChecked; DataItem=null; target element is 'DataSeries' (Name=''); target property is 'MarkerEnabled' (type 'Nullable`1')

Verso

For future users, you can run into this problem on a ContextMenu as well, no doubt for the same reason. – Fewness

I solved this by setting the DataContext of the parent item instead and binding to that. DataContext="{Binding ElementName=DisplayMarkers}" – Rochette

Answer 1

You might not have a namescope where you try to bind, you could try to replace the ElementName construct with Source={x:Reference DisplayMarkers}.

The gist of it is that if you have elements in XAML which are not in the visual or logical tree you will not be able to use certain bindings like RelativeSource and ElementName, I suspect that DataSeries is not in any tree either (it sure sounds like it's abstract).

For a workaround for potential cyclical dependency errors see: https://mcmap.net/q/277122/-how-to-hide-wpf-datagrid-columns-depending-on-a-property

Thresher

Exactly right. Thank you. That solved my problem. I don't really understand the issue with a namescope and why I need to do this. But it works for now. – Verso

@Hosea146: The gist of it is that if you have elements in XAML which are not in the visual or logical tree you will not be able to use certain bindings like RelativeSource and ElementName, i suspect that DataSeries is not in any tree either (it sure sounds like it's abstract). – Thresher

@H.B.:Sorry to hear that!Is there any solution in .net3.5? – Imponderable

@Claw: If you can create your own markup extensions in 3.5 (can't remember if that is the case) you might be able to somehow emulate the 4.0 x:Reference. – Thresher

This gives: Cannot call MarkupExtension.ProvideValue because of a cyclical dependency. Properties inside a MarkupExtension cannot reference objects that reference the result of the MarkupExtension. The affected MarkupExtensions are... Solution (unbelievable) is #32879383 – Jezabel

@dudeNumber4: I know, i mention it in most answers that relate to x:Reference, e.g. https://mcmap.net/q/277122/-how-to-hide-wpf-datagrid-columns-depending-on-a-property – Thresher

You should add the cyclical dependency comment into the answer. – Rochette

Answer 2

I'm guessing that the writer of Chart, when deriving from FrameworkElement or whatever, failed to realize that they needed to add any child elements to the logical tree either manually or through an override. You don't get that for free when deriving.

Breaking the logical tree breaks the ability of children to bind by ElementName.

If you are the author of the Chart object, you can see this related question and answer.

Drunken

Answer 3

For other readers, another possible cause is using a UserControl instead of a custom control for what's in the role of vf:Chart, above. I wrote a split button (in the role of the chart) and changing it from a UserControl to a custom control got my ElementName binding working.

Cenogenesis