xamarin ViewController add child helper

vc_child

private void AddViewControllerAsChild(UIViewController child, UIViewController parent)         {             child.WillMoveToParentViewController(parent);             parent.AddChildViewController(child);             parent.View.AddSubview(child.View);              child.DidMoveToParentViewController(parent);         }          private void RemoveChildViewController(UIViewController child)         {             child.WillMoveToParentViewController(null);             child.RemoveFromParentViewController();             child.View.RemoveFromSuperview();             child.DidMoveToParentViewController(null);         }