App.xaml

<Application x:Class="Localization_Demo.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:Localization_Demo"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="pack://application:,,,/Localization_Demo;component/Languages/zh-hans.xaml"/>
                <!--<ResourceDictionary Source="pack://application:,,,/Localization_Demo;component/Languages/zh-hant.xaml"/>-->
                <!--<ResourceDictionary Source="pack://application:,,,/Localization_Demo;component/Languages/en-us.xaml"/>-->
                <ResourceDictionary Source="pack://application:,,,/PresentationFramework.Fluent;component/Themes/Fluent.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>