I'm trying to learn GDI+ (in C#). CodeProject has this article which is a free chapter from the 2001 WROX book Professional C#. Is this still an advisable way to learn GDI+ or is a more modern resource preferable? If the latter, what would be such a resource?
AFAIK, GDI+ hasn't evolved too much since 2001, so I think this book is still relevant, although it might not contain the latest additions to the API.
Well, newer versions of .Net put layers on top of older layers, so all the older knowledge you get is definitely practicable, however not all of it is practical. There have been newer innovations which can be used to get better results.
GDI+ is quite contemporary and you can use it in your projects, but soon the entire Windowform model is going to be replaced by WPF or so Microsoft wishes. So if you want to put in a long-term investment in learning a new designing model for the Windows operating system I think you should invest in WPF. It has many shortcomings now, but they will be solved and it is the way to go if you're going to develop for the 'next' version of Windows.