bindable property for checkbox ischecked do not reflect when trigger used - wpf

Question

My bindable property RevalSurfaceChecked do not get updated when we set IsChecked property in trigger
<CheckBox Grid.Row="1" Grid.Column="2" Grid.ColumnSpan="2" x:Name="chkRevalSurface" Content="Export Reval Surface (if applicable)"
HorizontalAlignment="Left" VerticalAlignment="Center">
<CheckBox.IsEnabled>
<MultiBinding Converter="{StaticResource RevalSurfaceCheckboxEnableConverter}">
<Binding ElementName="ChkExportToCSV" Path="IsChecked"></Binding>
<Binding ElementName="chkExportToExcel" Path="IsChecked"></Binding>
</MultiBinding>
</CheckBox.IsEnabled>
<CheckBox.Style>
<Style TargetType="{x:Type CheckBox}">
<Setter Property="IsChecked" Value="{Binding RevalSurfaceChecked}" />
<Style.Triggers>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="IsChecked" Value="False"></Setter>
</Trigger>
</Style.Triggers>
</Style>
</CheckBox.Style>
</CheckBox>
The logic here is that if I check any of the two checkbox, then the chkRevalSurface should get enabled else stay disabled-written in converter. When chkRevalSurface is disabled it should be set unchecked (written in trigger) and RevalSurfaceChecked property should be set to False. if checked set it to True in viewmodel.
ButRevalSurfaceCheckedis not set to true or false.

Answer 1

The problem is that the <Setter Property="IsChecked" Value="False"></Setter> clears the original binding, so your CheckBox's IsChecked property just ends up being False without changing the underlying property.
You mentioned you have a viewmodel, I assume the ChkExportToCSV and chkExportToExcel CheckBoxes are bound to a property in your viewmodel.
Lets assume this viewmodel:
public class MainWindowViewModel : INotifyPropertyChanged
{
private bool _revalSurfaceChecked;
public bool RevalSurfaceChecked
{
get { return _revalSurfaceChecked; }
set
{
_revalSurfaceChecked = value;
OnPropertyChanged();
}
}
private bool _isChkExportToCSVChecked;
public bool IsChkExportToCSVChecked
{
get { return _isChkExportToCSVChecked; }
set
{
_isChkExportToCSVChecked = value;
RevalSurfaceChecked = RevalSurfaceChecked && (_isChkExportToCSVChecked || _ischkExportToExcelChecked);
OnPropertyChanged();
}
}
private bool _ischkExportToExcelChecked;
public bool IschkExportToExcelChecked
{
get { return _ischkExportToExcelChecked; }
set
{
_ischkExportToExcelChecked = value;
RevalSurfaceChecked = RevalSurfaceChecked && (_isChkExportToCSVChecked || _ischkExportToExcelChecked);
OnPropertyChanged();
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
if (PropertyChanged != null)
{
PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
And this XAML:
<CheckBox x:Name="ChkExportToCSV" Content="ChkExportToCSV" IsChecked="{Binding IsChkExportToCSVChecked}"
HorizontalAlignment="Left" VerticalAlignment="Center" />
<CheckBox x:Name="chkExportToExcel" Content="chkExportToExcel" IsChecked="{Binding IschkExportToExcelChecked}"
HorizontalAlignment="Left" VerticalAlignment="Center" />
<CheckBox x:Name="chkRevalSurface" Content="Export Reval Surface (if applicable)"
HorizontalAlignment="Left" VerticalAlignment="Center"
IsChecked="{Binding RevalSurfaceChecked}">
<CheckBox.IsEnabled>
<MultiBinding Converter="{StaticResource AnyTrueConverter}">
<Binding ElementName="ChkExportToCSV" Path="IsChecked"></Binding>
<Binding ElementName="chkExportToExcel" Path="IsChecked"></Binding>
</MultiBinding>
</CheckBox.IsEnabled>
</CheckBox>
I'm binding the ChkExportToCSV's IsChecked property to the IsChkExportToCSVChecked property in the viewmodel and the chkExportToExcel's IsChecked to the IschkExportToExcelChecked property.
I removed the Style from chkRevalSurface and for the IsEnabled I use a converter that gives back true if any of the inputs are true. I assume your RevalSurfaceCheckboxEnableConverter does the same, but I'll include it here:
public class AnyTrueConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
return values != null && values.OfType<bool>().Any(b => b);
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
The trick is in the setter of IsChkExportToCSVChecked and IschkExportToExcelChecked:
RevalSurfaceChecked = RevalSurfaceChecked && (_isChkExportToCSVChecked || _ischkExportToExcelChecked);
We moved the logic from the DataTrigger to here. This should solve your problem. I tested and it works for me.