Avalonia/samples/ControlCatalog/MainView.xaml

<UserControl x:Class="ControlCatalog.MainView"
             xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:controls="using:ControlSamples"
             xmlns:models="using:ControlCatalog.Models"
             xmlns:pages="using:ControlCatalog.Pages"
             xmlns:viewModels="using:ControlCatalog.ViewModels"
             x:DataType="viewModels:MainWindowViewModel">
  <Grid>
    <Grid.Styles>
      <Media Query="width >= 600">
        <Style  Selector="TextBlock#MinWidth">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="width >= 600 and height &lt;= 550 and orientation:portrait">
        <Style  Selector="TextBlock#Multi">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="width &lt;= 800">
        <Style  Selector="TextBlock#MaxWidth">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="height >= 600">
        <Style  Selector="TextBlock#MinHeight">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="height &lt;= 800">
        <Style  Selector="TextBlock#MaxHeight">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="orientation:landscape">
        <Style  Selector="TextBlock#Landscape">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="orientation:portrait">
        <Style  Selector="TextBlock#Portrait">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="platform:windows">
        <Style  Selector="TextBlock#Windows">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="platform:linux">
        <Style  Selector="TextBlock#Linux">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="platform:osx">
        <Style  Selector="TextBlock#OSX">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="platform:android">
        <Style  Selector="TextBlock#Android">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
      <Media Query="platform:ios">
        <Style  Selector="TextBlock#iOS">
          <Setter Property="Foreground"
                  Value="Red" />
        </Style>
      </Media>
    </Grid.Styles>
    <StackPanel Spacing="10">
      <TextBlock Name="MinWidth" Classes="h2" Text="width >= 600" />
      <TextBlock Name="MaxWidth" Classes="h2" Text="width &lt;= 800" />
      <TextBlock Name="Multi" Classes="h2" Text="width >= 600 and height &lt;= 550 and orientation:portrait" />
      <TextBlock Name="MinHeight" Classes="h2" Text="height >= 600" />
      <TextBlock Name="MaxHeight" Classes="h2" Text="height &lt;= 800" />
      <TextBlock Name="Landscape" Classes="h2" Text="orientation:landscape" />
      <TextBlock Name="Portrait" Classes="h2" Text="orientation:portrait" />
      <TextBlock Name="Windows" Classes="h2" Text="platform:windows" />
      <TextBlock Name="Linux" Classes="h2" Text="platform:linux" />
      <TextBlock Name="OSX" Classes="h2" Text="platform:osx" />
      <TextBlock Name="Android" Classes="h2" Text="platform:android" />
      <TextBlock Name="iOS" Classes="h2" Text="platform:ios" />
    </StackPanel>
  </Grid>
</UserControl>