I’m binding to a BindingList to a class that has a child BindingList for the details that show up in my Master-Detail grid.
Based on records in the user’s DB, some of master records don’t have any child records. I’ve searched high & low trying to figure out a way to hide or disable the expander when the master has no child rows.
I’ve provided my own Collapse/ExpandGroupGlyph (see XAML below) – it’d be great if I could somehow add binding to the Visibility property that somehow bound to the current row has child items or not.
I tried the following: http://forums.xceed.com/forums/topic/expander-visibility-issue/ – but there doesn’t seem to be a HasChildItems of the DataRow.
I tried pasting in the XAML using the code button, it won’t let me submit.
XAML code with the less than/greater than chars replaced with html codes:
<g:TableView.ExpandGroupGlyph>
<DataTemplate>
<!-- Not sure why the wonkiness, but getting the icon centered required a weird margin + wrapper grid. -->
<Grid x:Name="grd"
Width="24"
VerticalAlignment="Stretch"
Background="Transparent">
<Grid.Effect>
<DropShadowEffect BlurRadius="0"
RenderingBias="Performance"
ShadowDepth="1" />
</Grid.Effect>
<Border x:Name="brd"
Width="16"
Height="16"
Margin="3,12"
VerticalAlignment="Center"
BorderBrush="LightGray"
BorderThickness="1">
<Border.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=grd,
Path=IsMouseOver}"
Value="True">
<Setter Property="Border.Background"
Value="{DynamicResource appIconColor}" />
</DataTrigger>
</Style.Triggers>
</Style>
</Border.Style>
<Path Width="10"
Height="10"
Margin="1"
Data="M0,5 H10 M5,5 V10Z"
Stroke="White"
StrokeThickness="2" />
</Border>
</Grid>
</DataTemplate>
</g:TableView.ExpandGroupGlyph>I made a little progress on this one. I added a readonly property called HasChildRows to master item class that returns true if the count of the child binding list > 0.
I then was able to use FindAncestor and bind to the parent DataRow.DataContext.HasChildRows. This works, technically.
Visibility="{Binding Mode=OneWay,
RelativeSource={RelativeSource Mode=FindAncestor,
AncestorType={x:Type g:DataRow}},
Path=DataContext.HasChildRows,
Converter={StaticResource BooleanToVisibilityConverter}}"^ the problem with the above is at runtime, Visual Studio has a silent binding error for every new row that gets loaded:
System.Windows.Data Error: 4 : Cannot find source for binding with reference ‘RelativeSource FindAncestor, AncestorType=’Xceed.Wpf.DataGrid.DataRow’, AncestorLevel=’1”. BindingExpression:Path=DataContext.HasChildRows;
^ So it looks like binding is failing (at least at first) then succeeding. Is there a better way to bind so it isn’t failing at first. I’m just worried about performance if there is a bunch of rows from the master table are returned in query and every single row is going to initially fail it’s binding.