UserControl in DataTemplate does not apply font style

Question

I have a user control in a DataTemplate , Style for TextBlock does not change FontSize , but changes Background .

Attached examples:

• Create a WPF window.

• Create a UserControl1 User Control

• Inside the window, paste the code below:

   <Window.Resources> <Style TargetType="{x:Type TextBlock}" x:Key="TextBlockStyleFontAndBackgound"> <Setter Property="FontSize" Value="20" /> <Setter Property="Background" Value="Blue" /> </Style> <DataTemplate x:Key="contentTemplate"> <StackPanel> <m:UserControl1 /> </StackPanel> </DataTemplate> </Window.Resources> <Grid> <ContentControl FontSize="10"> <StackPanel x:Name="stackPanel"> <Button Click="Button_Click" /> <ContentControl ContentTemplate="{StaticResource contentTemplate}" /> <!--<m:UserControl1 />--> </StackPanel> </ContentControl> </Grid> 

• In user control, paste the following code:

   <UserControl.Resources> <DataTemplate x:Key="contentTemplateInsideUserControl"> <TextBlock Name="textBlockInResourse" Text="textBlockInsideUserControlResource" Style="{DynamicResource TextBlockStyleFontAndBackgound}"/> </DataTemplate> </UserControl.Resources> <Grid> <StackPanel> <ContentControl ContentTemplate="{StaticResource contentTemplateInsideUserControl}" /> <Button Content="St" Click="Button_Click" /> <TextBlock Name="textBlockInControl" Text="textBlockInsideUserControl" Style="{DynamicResource TextBlockStyleFontAndBackgound}" /> </StackPanel> </Grid> 

We have 2 text blocks with the same background color, blue, but with different font sizes.

textBlockInResourse FontSize = 20 , taken from the TextBlockStyleFontAndBackgound style

textBlockInControl FontSize = 10 , inherited value, why is this happening?

I added a handle to the user element:

  private void Button_Click(object sender, RoutedEventArgs e) { Style style = FindResource("TextBlockStyleFontAndBackgound") as Style; textBlockInControl.Style = null; textBlockInControl.Style = style; } 

And now the Font set to the TextBlockStyleFontAndBackgound style, and the size is 20

Why now FontSize is taken from the TextBlockStyleFontAndBackgound style.

Thanks Barak

Answer 1

This is a very strange problem that you found there. I'm not sure why FontSize not affected if not in the DataTemplate ... looking at two property descriptions and notes on MSDN, the only difference between the two is that TextBlock.FontSize also AttachedProperty , but I don't see how this will affect to anything.

However, I can offer a solution to the problem if you are still interested. Try declaring your Style in the App.xaml file:

 <Application.Resources> <Style TargetType="{x:Type TextBlock}" x:Key="TextBlockStyleFontAndBackgound"> <Setter Property="FontSize" Value="20" /> <Setter Property="Background" Value="Blue" /> </Style> </Application.Resources> 

Then declare your TextBlock in UserControl using StaticResource as follows:

 <TextBlock Text="text" Style="{StaticResource TextBlockStyleFontAndBackgound}" />