Saves any server control state changes that have occurred since the time the page was posted back to the server.
The server control's current state; otherwise, null.
Use the ChangePassword.SaveControlState method to save state information required for the operation of the System.Web.UI.WebControls.ChangePassword control. This control state data is stored separately from the view state data for the System.Web.UI.WebControls.ChangePassword control.
Custom controls using control state must call the System.Web.UI.Page.RegisterRequiresControlState(System.Web.UI.Control) method on the System.Web.UI.Control.Page object before saving control state.