Avalonia/samples/ControlCatalog/App.xaml

<Application xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:vm="using:ControlCatalog.ViewModels"
             x:DataType="vm:ApplicationViewModel"
             Name="Avalonia ControlCatalog"
             x:Class="ControlCatalog.App">
  <Application.Resources>
    <ResourceDictionary>
      <!-- Custom controls defined in other assemblies -->
      <ResourceDictionary.MergedDictionaries>
        <ResourceInclude Source="avares://ControlSamples/HamburgerMenu/HamburgerMenu.xaml" />
      </ResourceDictionary.MergedDictionaries>

      <!-- Resources used only in the control catalog -->
      <ResourceDictionary.ThemeDictionaries>
        <ResourceDictionary x:Key="Default">
          <Color x:Key="CatalogBaseLowColor">#33000000</Color>
          <Color x:Key="CatalogBaseMediumColor">#99000000</Color>
          <Color x:Key="CatalogChromeMediumColor">#FFE6E6E6</Color>
          <Color x:Key="CatalogBaseHighColor">#FF000000</Color>
        </ResourceDictionary>
        <ResourceDictionary x:Key="Dark">
          <Color x:Key="CatalogBaseLowColor">#33FFFFFF</Color>
          <Color x:Key="CatalogBaseMediumColor">#99FFFFFF</Color>
          <Color x:Key="CatalogChromeMediumColor">#FF1F1F1F</Color>
          <Color x:Key="CatalogBaseHighColor">#FFFFFFFF</Color>
        </ResourceDictionary>
      </ResourceDictionary.ThemeDictionaries>

      <!-- Styles attached dynamically depending on current theme (simple or fluent) -->
      <FluentTheme x:Key="FluentTheme" />
      <SimpleTheme x:Key="SimpleTheme" />
      <StyleInclude x:Key="ColorPickerFluent" Source="avares://Avalonia.Controls.ColorPicker/Themes/Fluent/Fluent.xaml" />
      <StyleInclude x:Key="ColorPickerSimple" Source="avares://Avalonia.Controls.ColorPicker/Themes/Simple/Simple.xaml" />
    </ResourceDictionary>
  </Application.Resources>
  <Application.Styles>
    <Style Selector="TextBlock.h1, TextBlock.h2, TextBlock.h3">
      <Setter Property="TextWrapping" Value="Wrap" />
    </Style>
    <Style Selector="TextBlock.h1">
      <Setter Property="FontSize" Value="16" />
      <Setter Property="FontWeight" Value="Medium" />
    </Style>
    <Style Selector="TextBlock.h2">
      <Setter Property="FontSize" Value="14" />
    </Style>
    <Style Selector="TextBlock.h3">
      <Setter Property="FontSize" Value="12" />
    </Style>
    <Style Selector="Label.h1">
      <Setter Property="FontSize" Value="16" />
      <Setter Property="FontWeight" Value="Medium" />
    </Style>
    <Style Selector="Label.h2">
      <Setter Property="FontSize" Value="14" />
    </Style>
    <Style Selector="Label.h3">
      <Setter Property="FontSize" Value="12" />
    </Style>
  </Application.Styles>
  <TrayIcon.Icons>
    <TrayIcons>
      <TrayIcon Icon="/Assets/test_icon.ico" MacOSProperties.IsTemplateIcon="true" ToolTipText="Avalonia Tray Icon ToolTip">
        <TrayIcon.Menu>
          <NativeMenu>
            <NativeMenuItem Header="Settings">
              <NativeMenu>
                <NativeMenuItem Header="Option 1" ToggleType="Radio" IsChecked="True" />
                <NativeMenuItem Header="Option 2" ToggleType="Radio" />
                <NativeMenuItemSeparator />
                <NativeMenuItem Header="Option 3" ToggleType="CheckBox" IsChecked="True" />
                <NativeMenuItem Icon="/Assets/test_icon.ico" Header="Restore Defaults" Command="{Binding RestoreDefault}" />
                <NativeMenuItem Header="Disabled option" IsEnabled="False" />
                <NativeMenuItem Header="Hidden option" IsVisible="False" />
              </NativeMenu>
            </NativeMenuItem>
            <NativeMenuItem Header="Exit" Command="{Binding ExitCommand}" />
          </NativeMenu>
        </TrayIcon.Menu>
      </TrayIcon>
    </TrayIcons>
  </TrayIcon.Icons>
</Application>