Style object based on binding bool attribute in wpf

Question

How can change the fill color of an object I\'m being to in my mvvm setup using xaml in wpf. I want to change the fill color to red when the attribute being bound to is set to

Answer 1

First of all you don't need any Binding for what you are trying to do. DataTrigger is enough. In the example below IsCyan is a boolean property of ViewModel. But Background of TextBlock is not bound at all.

           <TextBlock Text="Inside content">
                <TextBlock.Style>
                    <Style TargetType="TextBlock">
                        <Style.Triggers>
                            <DataTrigger Binding="{Binding IsCyan}" Value="True">
                                <Setter Property="Background" Value="DarkCyan"/>
                            </DataTrigger>
                            <DataTrigger Binding="{Binding IsCyan}" Value="False">
                                <Setter Property="Background" Value="DarkGoldenrod"/>
                            </DataTrigger>
                        </Style.Triggers>
                    </Style>
                </TextBlock.Style>
            </TextBlock>

But if at all you need Binding, solution by the user benPearce to use Converter is the way to go.

Answer 2

You need to use an IValueConverter on the binding.

BackgroundColor="{Binding Path=IsRound, Converter={StaticResource BoolToFillColorConverter}}"

public class BoolToFillColorConverter: IValueConverter
{
  public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
      bool b;
      if (bool.TryParse(value, out b))
      {
        if (b) return Red
        else return Blue;
      }
      else
      {
        return SomeDefaultColour;
      }
  public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
  {
    return null;
  }
}