Dependency Properties in WPF

I don't want to write a long blog entry, just to attract attention to this blog entry from Josh on WPF which is very concise, to the point and also directing to more complex articles that add more detail.

Even so, I want to cite a part which I think is essential to understanding the concept of Dependency Properties: Remember, a DP never really “has” a value…its value depends on various external factors. That’s why they are called dependency properties.