public ValidationDeactivatedState(BackgroundValidationSynchronizer <TValidationResult> parent)
     : base(parent)
 {
 }
 public IdleState(BackgroundValidationSynchronizer <TValidationResult> parent)
     : base(parent)
 {
 }
 public CancellingForDeactivationState(BackgroundValidationSynchronizer <TValidationResult> parent)
     : base(parent)
 {
 }
            public SynchronizerState(BackgroundValidationSynchronizer <TValidationResult> parent)
            {
                Fx.Assert(parent != null, "parent should not be null.");

                this.Parent = parent;
            }