How do I correctly bind a Popup to a ToggleButton?

Stephans answers has the disadvantage, that the desired behaviour of closing the popup whenever it loses focus also disappears.

I solved it by disabling the toggle-button when the popup is open. An alternative would be to use the IsHitTestVisible Property instead of is enabled:

    <ToggleButton x:Name="TogglePopupButton" Content="My Popup Toggle Button" Width="100"  IsEnabled="{Binding ElementName=ToggledPopup, Path=IsOpen, Converter={StaticResource BoolToInvertedBoolConverter}}"/>    <Popup x:Name="ToggledPopup" StaysOpen="False" IsOpen="{Binding IsChecked, ElementName=TogglePopupButton, Mode=TwoWay}">        <Border Width="100" Height="200" Background="White" BorderThickness="1" BorderBrush="Black">            <TextBlock>This is a test</TextBlock>        </Border>                    </Popup>

The converter looks like this:

public class BoolToInvertedBoolConverter : IValueConverter{    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)    {        if (value is bool)        {            bool boolValue = (bool)value;            return !boolValue;        }        else            return false;    }    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)    {        throw new NotImplementedException("ConvertBack() of BoolToInvertedBoolConverter is not implemented");    }}

Solution without IValueConverter:

<Grid>    <ToggleButton x:Name="TogglePopupButton" Content="My Popup Toggle Button" Width="100" >        <ToggleButton.Style>            <Style TargetType="{x:Type ToggleButton}">                <Setter Property="IsHitTestVisible" Value="True"/>                <Style.Triggers>                    <DataTrigger Binding="{Binding ElementName=Popup, Path=IsOpen}" Value="True">                        <Setter Property="IsHitTestVisible" Value="False"/>                    </DataTrigger>                </Style.Triggers>            </Style>        </ToggleButton.Style>    </ToggleButton>    <Popup StaysOpen="false" IsOpen="{Binding IsChecked, ElementName=TogglePopupButton, Mode=TwoWay}"               PlacementTarget="{Binding ElementName=TogglePopupButton}" PopupAnimation="Slide"            x:Name="Popup">        <Border Width="100" Height="200" Background="White" BorderThickness="1" BorderBrush="Black">            <TextBlock>This is a test</TextBlock>        </Border>    </Popup></Grid>

On the ToggleButton set the Property ClickMode="Press"apixeltoofar