Code inspection: Collection is never updated (non-private accessibility)

ReSharper analyzes access to collections created in your code and warns you if a collection is never filled or modified in the entire solution even if there is read access to this collection.

All standard collection types are analyzed this way by default. If necessary, you can also apply this analysis to your custom collections that derive from IEnumerable. In this case, you need to tell ReSharper how invocations of collection’s public methods will affect the contents of the collection. To do so, mark the methods of your collection class with the [CollectionAccessAttribute], which should have one of four flags: None, Read, ModifyExisitingContent, UpdatedContent (the difference between the last two flags is that UpdatedContent means that the marked function can also add new elements to the collection). Here is a simple example to illustrate this: