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

        internal protected virtual XPathNavigator CreateNavigator(XmlNode node)
        {
            XmlNodeType nodeType = node.NodeType;
            XmlNode parent;
            XmlNodeType parentType;

            switch (nodeType)
            {
                case XmlNodeType.EntityReference:
                case XmlNodeType.Entity:
                case XmlNodeType.DocumentType:
                case XmlNodeType.Notation:
                case XmlNodeType.XmlDeclaration:
                    return null;
                case XmlNodeType.Text:
                case XmlNodeType.CDATA:
                case XmlNodeType.SignificantWhitespace:
                    parent = node.ParentNode;
                    if (parent != null)
                    {
                        do
                        {
                            parentType = parent.NodeType;
                            if (parentType == XmlNodeType.Attribute)
                            {
                                return null;
                            }
                            else if (parentType == XmlNodeType.EntityReference)
                            {
                                parent = parent.ParentNode;
                            }
                            else
                            {
                                break;
                            }
                        }
                        while (parent != null);
                    }
                    node = NormalizeText(node);
                    break;
                case XmlNodeType.Whitespace:
                    parent = node.ParentNode;
                    if (parent != null)
                    {
                        do
                        {
                            parentType = parent.NodeType;
                            if (parentType == XmlNodeType.Document
                                || parentType == XmlNodeType.Attribute)
                            {
                                return null;
                            }
                            else if (parentType == XmlNodeType.EntityReference)
                            {
                                parent = parent.ParentNode;
                            }
                            else
                            {
                                break;
                            }
                        }
                        while (parent != null);
                    }
                    node = NormalizeText(node);
                    break;
                default:
                    break;
            }
            return new DocumentXPathNavigator(this, node);
        }

        public void Apply (XmlDocument targetDocument, IXmlNamespaceResolver context) {

            XPathExpression local_file_expression = file_expression.Clone();
            local_file_expression.SetContext(context);

            XPathExpression local_source_expression = source_expression.Clone();
            local_source_expression.SetContext(context);

            XPathExpression local_target_expression = target_expression.Clone();
            local_target_expression.SetContext(context);

            string file_name = (string) targetDocument.CreateNavigator().Evaluate(local_file_expression);
            string file_path = Path.Combine(root_directory, file_name);

            if (!File.Exists(file_path)) return;
            XPathDocument sourceDocument = new XPathDocument(file_path);

            XPathNavigator target_node = targetDocument.CreateNavigator().SelectSingleNode(local_target_expression);
            if (target_node == null) return;

            XPathNodeIterator source_nodes = sourceDocument.CreateNavigator().Select(local_source_expression);
            foreach (XPathNavigator source_node in source_nodes) {
                target_node.AppendChild(source_node);
            }
       
        }