How do I invert BooleanToVisibilityConverter?

Question

I'm using a BooleanToVisibilityConverter in WPF to bind the Visibility property of a control to a Boolean. This works fine, but I'd like one of the controls to hide if the boolean is true, and show if it's false.

Answer 1

Instead of inverting, you can achieve the same goal by using a generic IValueConverter implementation that can convert a Boolean value to configurable target values for true and false. Below is one such implementation:

public class BooleanConverter<T> : IValueConverter
{
    public BooleanConverter(T trueValue, T falseValue)
    {
        True = trueValue;
        False = falseValue;
    }

    public T True { get; set; }
    public T False { get; set; }

    public virtual object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value is bool && ((bool) value) ? True : False;
    }

    public virtual object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value is T && EqualityComparer<T>.Default.Equals((T) value, True);
    }
}

Next, subclass it where T is Visibility:

public sealed class BooleanToVisibilityConverter : BooleanConverter<Visibility>
{
    public BooleanToVisibilityConverter() : 
        base(Visibility.Visible, Visibility.Collapsed) {}
}

Finally, this is how you could use BooleanToVisibilityConverter above in XAML and configure it to, for example, use Collapsed for true and Visible for false:

<Application.Resources>
    <app:BooleanToVisibilityConverter 
        x:Key="BooleanToVisibilityConverter" 
        True="Collapsed" 
        False="Visible" />
</Application.Resources>

This inversion is useful when you want to bind to a Boolean property named IsHidden as opposed IsVisible.