Node.cs

        /// <summary>
        /// Insert a child at the given index.
        /// </summary>
        /// <param name="child">The child.</param>
        /// <param name="index">The index.</param>
        public void AddChildAt(CSSNode child, int index)
        {
            Insert(index, child);
            MarkUpdated();
            var node = (ReactShadowNode)child;

            if (!IsLeafNode)
            {
                var increase = node.IsLayoutOnly ? node._totalNativeChildren : 1;
                _totalNativeChildren += increase;

                UpdateNativeChildrenCountInParent(increase);
            }
        }

        /// <summary>
        /// Removes the child at the given index.
        /// </summary>
        /// <param name="index">The index.</param>
        public ReactShadowNode RemoveChildAt(int index)
        {
            var removed = RemoveAndReturnChildAt(index);

            MarkUpdated();

            if (!IsLeafNode)
            {
                var decrease = removed.IsLayoutOnly ? removed._totalNativeChildren : 1;
                _totalNativeChildren -= decrease;
                UpdateNativeChildrenCountInParent(decrease * -1);
            }

            return removed;
        }