Multibinding is the way!
Here how I solved:
<Setter Property="Foreground">
<Setter.Value>
<MultiBinding Converter="{StaticResource frgConverter}">
<Binding Path="state"/>
<Binding Path="color1"/>
<Binding Path="color2"/>
<Binding Path="color3"/>
</MultiBinding>
</Setter.Value>
</Setter>
And the Converter:
public class GridForegroundConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
int iColor;
int nState = System.Convert.ToInt32(values[0]);
if (nState < 0 || nState > 3)
throw new ArgumentOutOfRangeException("State");
iColor = System.Convert.ToInt32(values[nState + 1]);
byte[] bytes = BitConverter.GetBytes(iColor);
Color color = Color.FromRgb(bytes[2], bytes[1], bytes[0]);
return new SolidColorBrush(color);
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}