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

        internal override bool CanInsertBefore(XmlNode newChild, XmlNode refChild)
        {
            if (refChild == null)
                refChild = FirstChild;

            if (refChild == null)
                return true;

            switch (newChild.NodeType)
            {
                case XmlNodeType.XmlDeclaration:
                    return (refChild == FirstChild);

                case XmlNodeType.ProcessingInstruction:
                case XmlNodeType.Comment:
                    return refChild.NodeType != XmlNodeType.XmlDeclaration;

                case XmlNodeType.DocumentType:
                    {
                        if (refChild.NodeType != XmlNodeType.XmlDeclaration)
                        {
                            //if refChild is not the XmlDeclaration node, only need to go through the sibling before and including refChild to
                            //  make sure no Element ( rootElem node ) before the current position
                            return !HasNodeTypeInPrevSiblings(XmlNodeType.Element, refChild.PreviousSibling);
                        }
                    }
                    break;

                case XmlNodeType.Element:
                    {
                        if (refChild.NodeType != XmlNodeType.XmlDeclaration)
                        {
                            //if refChild is not the XmlDeclaration node, only need to go through the siblings after and including the refChild to
                            //  make sure no DocType node and XmlDeclaration node after the current position.
                            return !HasNodeTypeInNextSiblings(XmlNodeType.DocumentType, refChild);
                        }
                    }
                    break;
            }

            return false;
        }