System.Xml.XmlDocument.CanInsertAfter C# (CSharp) Method

        internal override bool CanInsertAfter(XmlNode newChild, XmlNode refChild)
        {
            if (refChild == null)
                refChild = LastChild;

            if (refChild == null)
                return true;

            switch (newChild.NodeType)
            {
                case XmlNodeType.ProcessingInstruction:
                case XmlNodeType.Comment:
                case XmlNodeType.Whitespace:
                case XmlNodeType.SignificantWhitespace:
                    return true;

                case XmlNodeType.DocumentType:
                    {
                        //we will have to go through all the siblings before the refChild just to make sure no Element node ( rootElem )
                        //  before the current position
                        return !HasNodeTypeInPrevSiblings(XmlNodeType.Element, refChild);
                    }

                case XmlNodeType.Element:
                    {
                        return !HasNodeTypeInNextSiblings(XmlNodeType.DocumentType, refChild.NextSibling);
                    }
            }

            return false;
        }