Accidental Singletons in Collection-Type Dependency Property

Dependency Properties are a unique and powerful feature of WPF/Silverlight though they are normally transparent to you and you will, for the most part, not worry about them. However, there are times when creating a Custom Dependency property will be the precise solution to your problem. Sometimes you will need to create a dependency property that is a collection-type. Now there is a very important point that you need to watch when creating a dependency property of this type, and that is the unintended creation of a singleton value.