Text color depends of value

Question

First of all, I am new to WPF and Xaml, so I just hope that you understand what I am asking.

I got this situation: There is a listBox of Animals. Every Animal has Weight property. What I am trying to achieve is whenever Weight of Animal is greater then 300 kg, that Weight should be displayed red.

Answer 1

You could use custom converter to achieve that. If your item looks like that:

public class Animal
{
    public int Weight { get; set; }
    public string Name { get; set; }
}

and ItemTemplate like that:

<DataTemplate x:Key="AnimalTemplate">
    <TextBlock Text="{Binding Name}" Foreground="{Binding Weight, Converter={StaticResource AnimalColorSelector}}"/>
</DataTemplate>

Your converter will be like the following one:

public class AnimalColorSelector : IValueConverter
{
    private readonly Color _overweightColor = Colors.Red;

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is int)
        {
            return (int) value > 300 ? new SolidColorBrush(_overweightColor) : Binding.DoNothing;
        }

        return Binding.DoNothing;
    }

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

This approach has the following pros:

1. You don't need to hardcode the default color, but inherit it by using Binding.DoNothing.
2. You don't need to store any style information in a view model.