WPF - Add Custom Font

I'm trying to add a custom font as a resource in my application. I have a "CustomFont" directory in the application and all the fonts inside of it are set to "Resource"

<Window.Resources>
    <Style x:Key="Gotham-XLight">
        <Setter Property="TextElement.FontFamily" 
                Value="/CustomFonts;Component/#Gotham-XLight" />
    </Style>
</Window.Resources>

And then on my TextBlock I have this: (inside a grid)

<TextBlock x:Name="TimeTextBlock" Style="{DynamicResource Gotham-XLight}" 
           TextAlignment="Center" FontSize="25" FontWeight="Bold" 
           Foreground="White" Text="TextBlockTimer" 
           Margin="105,242.974,0,226.975" HorizontalAlignment="Left" 
           Width="221.919" />

But I'm not seeing my font as people say. Am I doing something wrong?