CODEWITHSUNDEEP
.netwpfbinding
Bogdan Verbenets
Bogdan Verbenets

Reputation: 26952

formulas in WPF bindings

I have a combobox, and I want it to be enabled when checkbox is not checked. How do I write it? I tried following, but it seems that WPF doesn't recognise this syntax:

<ComboBox IsEnabled={Binding Path=!CheckBoxIsChecked, Mode=OneWay}/>
<CheckBox IsChecked={Binding Path=CheckBoxIsChecked}/>

Upvotes: 2

Views: 759

Answers (4)

Youp Bernoulli
Youp Bernoulli

Reputation: 5655

You should use so-called converters to do these kind of things. 

{Binding ElementName=CheckBox, Path=IsChecked, Converter=BoolToVisibilityConverter}

BoolToVisibilityConverter is a standard WPF converter. You can also easily write a OppositeBoolToVisibilityConverter. Many examples around on the net.

Upvotes: 1

emybob
emybob

Reputation: 1333

A trigger should work just as well for this:

   <CheckBox IsChecked="{Binding Path=CheckBoxIsChecked}" />
    <ComboBox Grid.Row="1" ItemsSource="{Binding Path=ComboItems}" SelectedItem="{Binding Path=SelectedItem, Mode=TwoWay}">
        <ComboBox.Style>
            <Style TargetType="ComboBox">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding Path=CheckBoxIsChecked}" Value="False" >
                        <Setter Property="IsEnabled" Value="True"/>
                    </DataTrigger>
                    <DataTrigger Binding="{Binding Path=CheckBoxIsChecked}" Value="True" >
                        <Setter Property="IsEnabled" Value="False"/>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </ComboBox.Style>
    </ComboBox>

Upvotes: -1

Maheep
Maheep

Reputation: 5605

You will have to use convertor to achieve this.

public class BooleanNegationConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return ConvertValue(value);
    }
    private bool ConvertValue(object value)
    {
        bool boolValue;
        if(!Boolean.TryParse(value.ToString(), out boolValue))
        {
            throw new ArgumentException("Value that was being converted was not a Boolean", "value");
        }
        return !boolValue;
    }
    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return ConvertValue(value);
    }
}

Then use it like this:

<ComboBox IsEnabled="{Binding Path=CheckBoxIsChecked, 
                              Mode=OneWay, 
                              Converter={StaticResource BooleanNegationConverterKey}}"/>

Remember you have to declare this static resource in xaml resources. Like this:

<UserControl.Resources>
    <ResourceDictionary>
        <BooleanNegationConverter x:Key="BooleanNegationConverterKey" />
    </ResourceDictionary>
</UserControl.Resources>

Upvotes: 1

Clemens
Clemens

Reputation: 128146

You will have to write a converter, i.e. a class that implements the IValueConverter interface. The converter will then be assigned to the Converter property of your binding:

<ComboBox IsEnabled="{Binding Path=CheckBoxIsChecked, Mode=OneWay, Converter={StaticResource MyConverter}}"/>

Upvotes: 1

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