Binding Fill property in class derived from Shape

I struggle with binding FillProperty in a classe derived from Shape.

public static readonly DependencyProperty NumberNodeProperty = DependencyProperty.Register("Number", typeof(int), typeof(MyDerivedShape), new FrameworkPropertyMetadata(0, FrameworkPropertyMetadataOptions.AffectsMeasure |      FrameworkPropertyMetadataOptions.AffectsParentMeasure));

public MyDerivedShape( DerivedViewModel viewmModel):Shape
{
   DataContext = viewmModel;

   Binding FillColorBinding = new Binding("FillColor");
   SetBinding(FillProperty, FillColorBinding);

   Binding numberBinding = new Binding("Number");
   SetBinding(NumberNodeProperty, numberBinding);
} 

"FillColor" property is declared in a base Viewmodel, from which DerivedViewModel inherits.

"Number" property is declared in DerivedViewModel

FillProperty is the default dependency property in Shape base class.

NumberNodeProperty is a dependency property declared in MyDerivedShape

So , what happens is that when I change "Number" in the DerivedViewModel, change is propagated to the Shape (the Shape draws a number)

But when I change FillColor in the DerivedVie开发者_如何学运维wModel, Change is not propagated, and color is not changed . I use FillColor is of type SolidColorBrush.

It seems that the binding does not work... Is it a consequence "Inherits" property set to false for "FillProperty" depedency property ?

I answer myself, because I found the answer :

In fact , in another piece of code in the application , I do something like this :

MyDerivedShape.Fill = Brushed.Red

This has huge consequences,as It destroys the Binding I put in place !

It is connected to "Dependency Property Value Precedence", a topic I was not aware at all.

So, if you bind a ViewModel Property to Dependency Property, you should never then set the Dependency Property directly. If you do so, your binding is lost !