Assembly: System.Web (in system.web.dll)
Return ValueReturns the server control's current view state. If there is no view state associated with the control, this method returns a null reference (Nothing in Visual Basic).
View state is the accumulation of the values of a server control's properties. These values are automatically placed in the server control's ViewState property, which is an instance of the StateBag class. The value of this property is then persisted to a string object after the save state stage of the server control life cycle.
When view state is saved, this string object is returned to the client as a variable that is stored in an Hidden HTML element. When you author custom server controls, you can improve efficiency by overriding this method and modifying your server control's ViewState property.