I’m using a ListBox with its DataTemplate containing a Canvas. I then bind the Left/Top of the Grid containing that Canvas to move it to a certain point.
I want to then have the child Grid centred at the X,Y coordinates I’ve specified, where the size of the child Grid is variable based on its content. I was planning on achieving this by using a TranslateTransform to move the Grid by half of its width.
I can’t see how I can set that TranslateTransform however as ElementName binding doesn’t work within a DataTemplate. Any ideas how I can achieve this?
<ItemsControl ItemsSource="{TemplateBinding SomeCollection}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Grid HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Canvas>
<Grid x:Name="Container"
Canvas.Left="{Binding X}"
Canvas.Top="{Binding Y}"
Background="#88000000">
<Grid.RenderTransform>
<TranslateTransform X="{Binding ActualWidth, ElementName=Container, Converter={StaticResource NegativeHalfConverter}}"
Y="{Binding ActualHeight, ElementName=Container, Converter={StaticResource NegativeHalfConverter}}" />
</Grid.RenderTransform>
<TextBlock Text="{Binding SomeValue}" FontSize="36" Foreground="White" />
</Grid>
</Canvas>
</DataTemplate>
</ItemsControl.ItemTemplate>
`
Looks like the fault wasn’t with the binding itself, but with a feature that means the ActualWidth/ActualHeight properties aren’t bindable. Thanks Filip.
To fix this I created a derived Grid with a couple of new dependency properties that I update in the SizeChanged events to have the ActualWidth/Height. I then use my DataTemplate as above, binding to these new DPs to translate and centre my Grid on a point. Seems to work a treat.