TextBlock in UserControl always gets style of light theme

Question

I have a user control like this (simplified): This control is constructed in code behind and assigned to the Header property of an Expander: ... The problem is that the textblocks inside the expander (and on the header) do not get the correct brushes for dark mode: As you can see, the controls above the expander behave as expected: The text blocks (1), text boxes (2) and comboboxes (3) all change appearance accordingly to the theme. But the text blocks in the expander do not (4, 5). Other controls inside the expander do work correctly (6, 7). Apart from the user control everything else is not styled explicitly but supposed to pick up the default Esri styles. The views above the expander and inside the expander are constructed dynamically in code behind - but both exactly the same way. Is there something I'm missing here?

vanesch · Answer

It looks like the TextBlock inside the Expander is inheriting the Expander's specified foreground color whereas the TextBlock sitting by itself is inheriting the foreground color of one of our Window controls.

You can try something like this.

var expander = new Expander();
      expander.Foreground = System.Windows.Media.Brushes.Green;

System.Windows.Style regularText = System.Windows.Application.Current.TryFindResource("RegularText") as System.Windows.Style;

var headerText = new TextBlock { Text = $"Expander-Header {ContentObject}" };
      headerText.Style = regularText; // text will be green otherwise
      expander.Header = headerText;

var content = new TextBlock { Text = $"In Expander {ContentObject}" };
      content.Style = regularText; // text will be green otherwise
      expander.Content = content;

alehmann · Answer

Hi @CharlesMacleod, thanks for getting back to me on this. I prepared a small repro project that demonstrates the problem. I admit that it's a bit convoluted in how the UI is constructed, but I don't see how it's doing anything wrong. For reference, this is what the control looks like in light theme and dark theme:

control in light modecontrol in dark mode

ReproMissingStyle.zip

CharlesMacleod · Answer

do u mind providing your usercontrol xaml or some xaml that provides a repro and I'll forward to the UI team