DependencyProperty

Sometimes it is necessary to bind to a custom property on a Silverlight Control.  In order for that to work properly, you need to set it up as a DependencyProperty. 

public int Denominator
{
    get { return (int)this.GetValue(DenominatorProperty); }
    set { this.SetValue(DenominatorProperty, value); }
}

public static readonly DependencyProperty DenominatorProperty
    = DependencyProperty.Register(
            "Denominator", //Property Name
            typeof(int), //Property Type
            typeof(QualitativeStatusIndicator),  // type of Control
            new PropertyMetadata(
                 0, // default value
                 Denominator_PropertyChangedCallback));  // callback

private static void Denominator_PropertyChangedCallback(
    DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    QualitativeStatusIndicator myControl
       = d as QualitativeStatusIndicator;
    myControl.SetStatus();
}