styles.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
                    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
                    xmlns:pd="using:TestApp.Converters"
                    mc:Ignorable="d">
    <!-- Other styles omitted for clarity -->
    <pd:BackgroundValueConverter x:Key="BackgroundValueConverter"></pd:BackgroundValueConverter>
</ResourceDictionary>