Avalonia/samples/ControlCatalog/Pages/ToolTipPage.xaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="ControlCatalog.Pages.ToolTipPage">
    <StackPanel Orientation="Vertical"
                Spacing="4">
        <TextBlock Classes="h2">A control which pops up a hint when a control is hovered</TextBlock>

        <Grid RowDefinitions="Auto,Auto,Auto,Auto"
              ColumnDefinitions="Auto,Auto"
              Margin="0,16,0,0"
              HorizontalAlignment="Center">
            <ToggleSwitch Margin="5" 
                    HorizontalAlignment="Center"
                    IsChecked="{Binding Path=(ToolTip.ServiceEnabled), RelativeSource={RelativeSource AncestorType=UserControl}}"
                    Content="Enable ToolTip service" />
            <Border Grid.Column="0"
                    Grid.Row="1"
                    Background="{DynamicResource SystemAccentColor}"
                    Margin="5"
                    Padding="50"
                    ToolTip.Tip="This is a ToolTip">
                <TextBlock>Hover Here</TextBlock>
            </Border>
            <ToggleSwitch Grid.Column="1"
                      Margin="5"
                      Grid.Row="0"
                      IsChecked="{Binding ElementName=Border, Path=(ToolTip.IsOpen)}"
                      HorizontalAlignment="Center"
                      Content="ToolTip Open" />
            <Border Name="Border"
                    Grid.Column="1"
                    Grid.Row="1"
                    Background="{DynamicResource SystemAccentColor}"
                    Margin="5"
                    Padding="50"
                    ToolTip.Placement="Bottom">
                <ToolTip.Tip>
                    <StackPanel>
                        <TextBlock Classes="h1">ToolTip</TextBlock>
                        <TextBlock Classes="h2">A control which pops up a hint when a control is hovered</TextBlock>
                    </StackPanel>
                </ToolTip.Tip>
                <TextBlock>ToolTip bottom placement</TextBlock>
            </Border>
            <Border Grid.Row="2"
                    Background="{DynamicResource SystemAccentColor}"
                    Margin="5"
                    Padding="50"
                    ToolTip.Tip="Hello"
                    ToolTip.Placement="Top">
              <Border.Styles>
                <Style Selector="Border">
                  <Style.Animations>
                    <Animation Duration="0:0:2" IterationCount="Infinite">
                      <KeyFrame KeyTime="0:0:0">
                        <Setter Property="ToolTip.HorizontalOffset" Value="0" />
                        <Setter Property="ToolTip.VerticalOffset" Value="-50" />
                      </KeyFrame>
                      <KeyFrame KeyTime="0:0:2" >
                        <Setter Property="ToolTip.HorizontalOffset" Value="100" />
                        <Setter Property="ToolTip.VerticalOffset" Value="50" />
                      </KeyFrame>
                    </Animation>
                  </Style.Animations>
                </Style>
              </Border.Styles>
              <TextBlock>Moving offset</TextBlock>
            </Border>

            <Button Grid.Row="2" Grid.Column="1"
                    IsEnabled="False"
                    ToolTip.ShowOnDisabled="True"
                    ToolTip.Tip="This control is disabled"
                    Margin="5"
                    Padding="50">
              <TextBlock>ToolTip on a disabled control</TextBlock>
            </Button>

          <Border Grid.Row="3"
                  Grid.Column="0"
                  Background="{DynamicResource SystemAccentColor}"
                  Margin="5"
                  Padding="50"
                  ToolTip.Tip="Outer tooltip">
            <TextBlock Background="{StaticResource SystemAccentColorDark1}" Padding="10" ToolTip.Tip="Inner tooltip" VerticalAlignment="Center">Nested ToolTips</TextBlock>
          </Border>
            
          <Border Grid.Row="3"
                  Grid.Column="1"
                  Background="{DynamicResource SystemAccentColor}"
                  Margin="5"
                  Padding="50"
                  ToolTip.ToolTipOpening="ToolTipOpening"
                  ToolTip.Tip="Should never be visible">
            <TextBlock VerticalAlignment="Center">ToolTip replaced on the fly</TextBlock>
          </Border>
        </Grid>
    </StackPanel>
</UserControl>