Style assignment in the axml file
<TextBlock Hello" Style="{StaticResource MyTextBlockStyleName}" />
Style definition if in App.xaml
<Style x:Key="MyTextBlockStyleName" TargetType="TextBlock">
<Setter Property="FontFamily" Value="Arial"/>
<Setter Property="FontWeight" Value="Bold"/>
<Setter Property="Foreground" Value="White"/>
<Setter Property="FontSize" Value="18"/>
<Setter Property="Height" Value="24"/>
</Style>
It needs to be in a Application.Resources section, like this:
<Application
x:Class="MyApp.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:MyApp"
RequestedTheme="Light">
<Application.Resources>
<Style x:Key="MyTextBlockStyleName" TargetType="TextBlock">
<Setter Property="FontFamily" Value="Arial"/>
<Setter Property="FontWeight" Value="Bold"/>
<Setter Property="Foreground" Value="White"/>
<Setter Property="FontSize" Value="18"/>
<Setter Property="Height" Value="24"/>
</Style>
Other styles...
</Application.Resources>
</Application>
Style definition if in the axml file
Typically placed before the <grid>
<ContentDialog.Resources>
<Style x:Key="MyTextBlockStyleName" TargetType="TextBlock">
<Setter Property="FontFamily" Value="Arial"/>
<Setter Property="FontWeight" Value="Bold"/>
<Setter Property="Foreground" Value="White"/>
<Setter Property="FontSize" Value="18"/>
<Setter Property="Height" Value="24"/>
</Style>
</ContentDialog.Resources>
Feel free to comment if you can add help to this page or point out issues and solutions you have found. I do not provide support on this site, if you need help with a problem head over to stack overflow.