xaml中使用MultiBinding绑定多个属性

<Window.Resources>
    <local:SpecialFeaturesConverter x:Key="SpecialFeaturesConverter" />
    <local:BooltoVisibilityConvertor x:Key="InputToVisibility" />
    <ControlTemplate x:Key="ValidationTemplate">
        <DockPanel>
            <TextBlock Foreground="Red" FontSize="20">!</TextBlock>
            <AdornedElementPlaceholder />
        </DockPanel>
    </ControlTemplate>
</Window.Resources>

<TextBlock Text="Type Item Description" Margin="10,5,5,6" Grid.Column="1" Grid.Row="1">
    <TextBlock.Visibility>
        <MultiBinding Converter="{StaticResource InputToVisibility}">
            <Binding ElementName="DescriptionEntryForm" Path="Text.IsEmpty" />
            <Binding ElementName="DescriptionEntryForm" Path="IsFocused"/>
        </MultiBinding>
    </TextBlock.Visibility>
    <TextBlock.Foreground>
        <SolidColorBrush Opacity="0.5" Color="Black"/>
    </TextBlock.Foreground>
</TextBlock>

Converter

public class BooltoVisibilityConvertor : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        bool hasText = !(bool)values[0];
        bool hasFocus = (bool)values[1];

        if (hasText || hasFocus)
        {
            return Visibility.Collapsed;
        }
        return Visibility.Visible;
    }
    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}