public class AirCCLayer : Control
{
    public static readonly DependencyProperty AzimutProperty;

    static AirCCLayer()
    {
        FrameworkPropertyMetadata metadata;

        metadata = new FrameworkPropertyMetadata(20);
        metadata.AffectsRender = true;
        AzimutProperty = DependencyProperty.Register("Azimut", typeof(double), typeof(AirCCLayer), metadata); // тут ошибка выскакивает
    }

    public double Azimut
    {
        get { return (double)GetValue(AzimutProperty); }
        set { SetValue(AzimutProperty, value); }
    }
}