How to bind a property to false value

Question

I would like to bind the IsEnabled property of a ComboBox to the IsChecked property of a checkbox, while I want the ComboBox to be ENABLED only when the checkbox value is FALSE.

IsEnabled="{Binding ElementName=RegexCbx, Path=IsChecked}"

What's the simplest way for doing that?

Answer 1

Use style trigger:

<StackPanel>
    <CheckBox x:Name="Foo" Content="Click me"/>
    <ComboBox>
        <ComboBox.Style>
            <Style TargetType="{x:Type ComboBox}">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding IsChecked, ElementName=Foo}" Value="True">
                        <Setter Property="IsEnabled" Value="False"/>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </ComboBox.Style>
    </ComboBox>
</StackPanel>

Answer 2

A class derived from IValueConverter should do the trick:

public class BoolToOppositeBoolConverter : IValueConverter
{
    #region IValueConverter Members

    public object Convert(object value, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        if (targetType != typeof(bool))
            throw new InvalidOperationException("The target must be a boolean");

        return !(bool)value;
    }

    public object ConvertBack(object value, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        throw new NotSupportedException();
    }

    #endregion

}

Preferably in a Resource Dictionary, create an instance of the converter:

<converters:BoolToOppositeBoolConverter x:Key="oppositeBoolConverter" />

Then in your view, do something like this where the bool value for IsChecked gets converted to the opposite value. Don't forget to include the resource dictionary as a resource for the view.

<TextBox IsEnabled="{Binding IsChecked, Converter={StaticResource oppositeBoolConverter}" />

Answer 3

Another way to do that, is to use Blend 's DataTrigger :

    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
    xmlns:ie="http://schemas.microsoft.com/expression/2010/interactions"

    <ComboBox>
        <i:Interaction.Triggers>
            <ie:DataTrigger Binding="{Binding IsChecked, ElementName=RegexCbx}"
                            Value="False">
                <ie:ChangePropertyAction PropertyName="IsEnabled"
                                         TargetObject="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=ComboBox}}"
                                         Value="True"/>
            </ie:DataTrigger>
            <ie:DataTrigger Binding="{Binding IsChecked, ElementName=RegexCbx}"
                            Value="True">
                <ie:ChangePropertyAction PropertyName="IsEnabled"
                                         TargetObject="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=ComboBox}}"
                                         Value="False"/>
            </ie:DataTrigger>
        </i:Interaction.Triggers>
    </ComboBox>