System.Windows.DependencyProperty.InvokeChangedCallback C# (CSharp) Method

        static void InvokeChangedCallback(DependencyObject obj, DependencyProperty property, PropertyChangedCallback callback,
						   object old_obj, object new_obj)
        {
            if (old_obj == null && property.property_type.IsValueType && !property.IsNullable) {
                old_obj = property.GetDefaultValue (obj);
                Console.WriteLine ("WARNING: Got a null value for {0}.{1} which is a value type", property.DeclaringType.Name, property.Name);
            }

            if (Helper.AreEqual (property.PropertyType, old_obj, new_obj))
                return;

            var args = new DependencyPropertyChangedEventArgs (old_obj, new_obj, property);

            // note: since callbacks might throw exceptions but we cannot catch them
            callback (obj, args);
        }