WPF MVVM hiding button using BooleanToVisibilityConverter

Question

In my WPF application I am trying to change the visibility of a button depending on the options chosen by a user. On load I want one of the buttons to not be visible. I am using the in built value converter BooleanToVisibilityConverter. However it's not working as the button is appearing at load time. I have changed the property to both true and false, makes no difference. Below is my code, I can't see what I'm missing?

The property in my View Model

 bool ButtCancel
    {
        get { return _buttCancel; }
        set
        {
            _buttCancel = value;
            OnPropertyChanged("ButtCancel");
        }
    }

In my app.xaml

 <Application.Resources>       
    <BooleanToVisibilityConverter x:Key="BoolToVis"/>

In my MainWindow.xaml

 <Button Grid.Column="2" 
      Command="{Binding CommandButtProgressCancel}" 
      Content="Cancel" 
      Visibility="{Binding ButtCancel, Converter={StaticResource BoolToVis}}"
      IsEnabled="{Binding ButtCancelEnabled}" 
      Height="50" Width="120" 
      HorizontalAlignment="Center" 
      VerticalAlignment="Center" Margin="0,0,50,20"/>

Is your `ButtCancel` property `public`? It has no access modifier in your code excerpt, which would make it `private` and thus invisible to the binding engine. Also, you should not be binding the `IsEnabled` property; let the button use your command's `CanExecute` callback to determine its own state. — Mike Strobel, Dec 13 '13 at 15:39
@MikeStrobel, surely the default access modifier is `internal` and not `private`. — Sheridan, Dec 13 '13 at 15:49
@Sheridan For top-level declarations, the default is `internal`; for class members, including nested type declarations, it is `private`. — Mike Strobel, Dec 13 '13 at 15:57

Stefan Z Camilleri · Accepted Answer · 2013-12-13T16:13:41.197

51

For starters mate, if you're using a Command, then you don't need to bind IsEnabled, the command implementation should decide this.

Secondly, the binding of a ViewModel to a View tends to happen at a bit of a later stage, so it's best to also set a default value for the binding, like so

Visibility="{Binding ButtCancel, Converter={StaticResource BoolToVis}, FallbackValue=Hidden}"

Third, as Mike pointed out, ensure that your property is public, since the ViewModel and the View are two separate classes.

edited Dec 13 '13 at 16:13

answered Dec 13 '13 at 15:44

Stefan Z Camilleri

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An `internal` property won't work either. The binding engine has no knowledge of where a binding was declared, so all non-public members are treated the same (effectively `private`). – Mike Strobel Dec 13 '13 at 16:05
Oh, I wasn't aware of that, thanks Mike, I'll adjust my answer. – Stefan Z Camilleri Dec 13 '13 at 16:13

score 7 · Answer 2 · edited Nov 07 '18 at 09:55

Instead of using a converter, you can just use a DataTrigger.

<Button Grid.Column="2" Command="{Binding CommandButtProgressCancel}" Content="Cancel" 
        Visibility="{Binding ButtCancel, Converter={StaticResource BoolToVis}}" 
        IsEnabled="{Binding ButtCancelEnabled}" Height="50" Width="120"
        HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,0,50,20">
    <Button.Style>
        <Style TargetType={X:Type Button}>
            <!-- This would be the default visibility -->
            <Setter Property="Visibility" Value="Visible" />
            <Style.Triggers>
                <DataTrigger Binding="{Binding ButtCancel, UpdateSourceTrigger=PropertyChanged}" Value="True">
                    <Setter Property="Visibility" Value="Hidden" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </Button.Style>
</Button>

Update your ViewModel's properties to public

public bool ButtCancel
{
    get { return _buttCancel; }
    set
    {
        _buttCancel = value;
        OnPropertyChanged("ButtCancel");
    }
}

And make sure the DataContext of your MainWindow is set to the ViewModel.

triggers aren't the best if you are trying to use a MVVM pattern (as the OP says). — 00jt, Aug 13 '15 at 13:48

WPF MVVM hiding button using BooleanToVisibilityConverter

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