Animating Width/Height to an auto value

I always had problems when animating the Width and Height if these properties
were not explicitly set (which often you don't want). The main problem is
that the property is set to "NaN" which cannot be animated by
DoubleAnimation. You get the following exception:

Cannot animate the 'Height' property on a 'xxx' using a
'System.Windows.Media.Animation.DoubleAnimation'.

The workaround of using a ScaleTransform didn't work out fine for my
situation, so I decided to override the MeasureOverride method and add some
dependency properties to allow animating the Height and Width of controls
that use the Auto value.

Details can be found on my blog on http://blog.ramondeklein.nl/?p=16.