To reduce page bloat, we move view state to session state, rather than store it in hidden fields. This is done by overriding System.Web.UI.Page’s LoadPageStateFromPersistenceMedium() and SavePageStateToPersistenceMedium() methods.
protected override object LoadPageStateFromPersistenceMedium()
protected override void SavePageStateToPersistenceMedium(object state)
Session[“__ViewState”] = state;