Applications = code + markup

Got first really good WPF book of Charles Petzold "Applications = Code + Markup", BUT what's going on with code samples? Let's take a look: In MedievalButton example (as well as all over the samples) author using InvalidateVisual() method in each possible hole. What do you think will happend with performance? I'm not very experienced in WPF, but prety know CPP and C# programming. Invalidate context each time is VERY BAD CONCEPT, but maybe I'm wrong

So, WPF

So, WPF. After long delay, I started the MS-SAP project. It's promise to be very interesting, but who knows?

First

Let's see what we have here?