Updating DependencyProperty Metadata
What is the technical reason for not being able to update a DependencyProperty's metadata after it has already been set? 

If you try to do something similar to below it will generate an exception saying: 

> Cannot change property metadata after it has been associated with a property.

    MyProperty.DefaultMetata.PropertyChangedCallback = 
        new PropertyChangedCallback(MyMethod);
Updating DependencyProperty Metadata
===

What is the technical reason for not being able to update a DependencyProperty's metadata after it has already been set? 

If you try to do something similar to below it will generate an exception saying: 

> Cannot change property metadata after it has been associated with a property.

    MyProperty.DefaultMetata.PropertyChangedCallback = 
        new PropertyChangedCallback(MyMethod);