WPF 属性改变回调（Property Changed Callbacks）或依赖属性的注册，通常会使用静态方法

public double Value
{
    get { return (double)GetValue(ValueProperty); }
    set { SetValue(ValueProperty, value); }
}

public static readonly DependencyProperty ValueProperty =
    DependencyProperty.Register("Value", typeof(double), typeof(CircularProgressBar), new PropertyMetadata(0d, new PropertyChangedCallback(OnPropertyChanged)));

这里依赖属性的回调方法要使用静态的，同时依赖属性也是静态的