Wpf, style is not being applied

Question

I\'ve written a user control with popup, who\'s content is being set outside the control. The ControlTemplate of that control looks like the following:

Answer 1

Had a similar issue caused by another problem:

There is a strange bug in WPF that prevents styles, defined in merged dictionaries, from being applied to the first element:

https://www.engineeringsolutions.de/wpf-fix-style-is-only-applied-to-first-element/

Answer 2

Maybe you have some TextBlock style defining that it shouldd take the parent's control foreground.

Did you try to add a BasedOn property like this ?

<Style TargetType="TextBlock" BasedOn="{StaticResource {x:Type TextBlock}}">
  <Setter Property="Foreground" Value="#575757" />
</Style>

Answer 3

As a suggestion, shouldn't this:

TargetType="local:InfoIcon"

be like this?

TargetType="{x:Type local:InfoIcon}"

Answer 4

Edit2

I've set the Foreground of the UserControl to something else. This behavior is because the child TextBlock controls of the UserControl inherit the Foreground-Settings somehow. This has nothing to do with the popup or some other approaches we tried yet.

I've stumbled upon another question with a similar problems here: Cannot override controls foreground colour in wpf

I suggest to accept this strange behavior and just set a Foreground Color of the UserControl instead:

<Style TargetType="{x:Type local:InfoIcon}">
    <Setter Property="Foreground" Value="Red"/>
</Style>

previous Edit

You had my curiousity with this weird behavior, but after looking at your PoC it was rather obvious :) The Popup has some attached Properties TextElement.* where you can style the text elements in the popup. This was new to me, too and I will reseach a bit more afterwards. Nevertheless: Workaround for your Problem is to not style the TextBlock but the Popup instead. your code could look something like following :

<ControlTemplate TargetType="{x:Type local:InfoIcon}">
      <ControlTemplate.Resources>
        <Style TargetType="Popup">
          <Setter Property="TextElement.Foreground" Value="Red"/>
        </Style>
        <Style TargetType="Label">
          <Setter Property="Foreground" Value="Red" />
        </Style>
      </ControlTemplate.Resources>

      <Grid>
        <ToggleButton x:Name="TB" Width="16" Height="16"/>
        <Popup Placement="Bottom" PlacementTarget="{Binding ElementName=TB}" IsOpen="{Binding ElementName=TB, Path=IsChecked}" StaysOpen="False">
          <ContentPresenter Content="{TemplateBinding InfoContent}"/>
        </Popup>
      </Grid>
    </ControlTemplate>

I changed the styles to be outside of the controls, of course you can just use the attached properties of the popup directly. But initially you wanted to know how it works with the styles attached at the border, it does not matter now where you add the styles. You can use a ResourceDictionary for example.

Answer 5

I tried with your code example and this works :

 <ContentPresenter Content="{TemplateBinding InfoContent}">
                                <ContentPresenter.Style>
                                    <Style TargetType="{x:Type ContentPresenter}">
                                        <Setter Property="TextBlock.Foreground" Value="Red" />
                                    </Style>
                                </ContentPresenter.Style>
                                <ContentPresenter.Resources>
                                    <Style TargetType="{x:Type Label}">
                                        <Setter Property="Foreground" Value="Red" />
                                    </Style>
                                </ContentPresenter.Resources>
                            </ContentPresenter>

That's kind of odd because when I put the Foreground setter for the Label control inside the ContentPresenter.Style then this time it's Label wich doesn't work...I think it's because Label is a considered as a ContentControl whereas TextBlock is just a FrameworkElement.

Answer 6

I received answer on Microsoft forums; I'll leave it here in case someone encounters the same problem.

The difference is that a TextBlock is not a control, i.e. it doesn't have any ControlTemplate and because of this the implicit style doesn't get applied to it when it is located inside the StackPanel. Please see the following page for more information: http://blogs.msdn.com/b/wpfsdk/archive/2009/08/27/implicit-styles-templates-controls-and-frameworkelements.aspx

You could use Label elements or set the style for the TextBlock elements explicitly.

-- Magnus (MM8)