LaDOSE/LaDOSE.Src/LaDOSE.DesktopApp/App.xaml

<Application x:Class="LaDOSE.DesktopApp.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:LaDOSE.DesktopApp"
             >
    <Application.Resources>

        <ResourceDictionary>
                <ResourceDictionary.MergedDictionaries>
                    <ResourceDictionary>
                    <local:Bootstrapper x:Key="Bootstrapper" />
                    </ResourceDictionary>
                    <ResourceDictionary Source="Themes\Styles.xaml" />
            </ResourceDictionary.MergedDictionaries>
            </ResourceDictionary>
    </Application.Resources>
</Application>