问WPF工具提示可见性

EN

<Button 
  x:Name="btnAdd" 
  Content="Add" 
  ToolTipService.ShowOnDisabled="True" 
  ToolTipService.IsEnabled="{Binding ElementName=btnAdd, Path=IsEnabled, Converter={StaticResource boolToOppositeBoolConverter}}" 
  ToolTip="Appointments cannot be added whilst the event has outstanding changes."/>

<StackPanel Orientation="Vertical" HorizontalAlignment="Center" VerticalAlignment="Center">
    <CheckBox Name="chkDisabler" Content="Enable / disable button" Margin="10" />
    <Button Content="Hit me" Width="200" Height="100" IsEnabled="{Binding ElementName=chkDisabler, Path=IsChecked}">
        <Button.Style>
            <Style TargetType="{x:Type Button}">
                <Setter Property="ToolTipService.ShowOnDisabled" Value="true" />
                <Setter Property="ToolTip" Value="{x:Null}" />
                <Style.Triggers>
                    <Trigger Property="IsEnabled" Value="False">
                        <Setter Property="ToolTip" Value="Hi, there! I'm disabled!" />
                    </Trigger>
                </Style.Triggers>
            </Style>
        </Button.Style>
    </Button>
</StackPanel>