Gets a collection of keys representing the items in the System.Web.UI.StateBag object.
a ICollection
These keys are the names of the control properties. For example, if you created a BGColor property on a Table control that you customized, a BGColor entry is created in this collection representing that property on your Table control.
These keys correspond to the names of the System.Web.UI.StateItem objects stored in the System.Web.UI.StateBag collection for the current page or server control.
You can iterate over this collection using the StateBag.GetEnumerator method.