public IDisposable RegisterChangeCallback(Action<object> callback, object state)
 {
     Registration = new TokenCallbackRegistration()
     {
         RegisteredCallback = callback,
         RegisteredState = state,
     };
     return Registration;
 }
 public IDisposable RegisterChangeCallback(Action <object> callback, object state)
 {
     Registration = new TokenCallbackRegistration()
     {
         RegisteredCallback = callback,
         RegisteredState    = state,
     };
     return(Registration);
 }