mono/mcs/class/System.XML/System.Xml/XmlDocument.cs

//
// System.Xml.XmlDocument
//
// Authors:
//   Daniel Weber ([email protected])
//   Kral Ferch <[email protected]>
//   Jason Diamond <[email protected]>
//   Miguel de Icaza ([email protected])
//   Duncan Mak ([email protected])
//   Atsushi Enomoto ([email protected])
//
// (C) 2001 Daniel Weber
// (C) 2002 Kral Ferch, Jason Diamond, Miguel de Icaza, Duncan Mak,
//   Atsushi Enomoto
//

using System;
using System.IO;
using System.Text;
using System.Xml.XPath;
using System.Diagnostics;
using System.Collections;
using Mono.Xml;
using Mono.Xml.Native;

namespace System.Xml
{
	public class XmlDocument : XmlNode
	{
		#region Fields

		XmlNameTable nameTable;
		string baseURI = String.Empty;
		XmlImplementation implementation;
		bool preserveWhitespace = false;
		XmlResolver resolver;
		Hashtable idTable = new Hashtable ();

		// MS.NET rejects undeclared entities _only_ during Load(),
		// while ReadNode() never rejects such node. So it signs
		// whether we are on Load() or not (MS.NET uses Loader class,
		// but we don't have to implement Load() as such)
		bool loadMode;

		#endregion

		#region Constructors

		public XmlDocument () : this (null, null)
		{
		}

		protected internal XmlDocument (XmlImplementation imp) : this (imp, null)
		{
		}

		public XmlDocument (XmlNameTable nt) : this (null, nt)
		{
		}

		XmlDocument (XmlImplementation impl, XmlNameTable nt) : base (null)
		{
			if (impl == null)
				implementation = new XmlImplementation ();
			else
				implementation = impl;

			nameTable = (nt != null) ? nt : implementation.InternalNameTable;
			AddDefaultNameTableKeys ();
			resolver = new XmlUrlResolver ();
		}
		#endregion

		#region Events

		public event XmlNodeChangedEventHandler NodeChanged;

		public event XmlNodeChangedEventHandler NodeChanging;

		public event XmlNodeChangedEventHandler NodeInserted;

		public event XmlNodeChangedEventHandler NodeInserting;

		public event XmlNodeChangedEventHandler NodeRemoved;

		public event XmlNodeChangedEventHandler NodeRemoving;

		#endregion

		#region Properties

		public override string BaseURI {
			get {
				return baseURI;
			}
		}

		public XmlElement DocumentElement {
			get {
				XmlNode node = FirstChild;

				while (node != null) {
					if (node is XmlElement)
						break;
					node = node.NextSibling;
				}

				return node != null ? node as XmlElement : null;
			}
		}

		public virtual XmlDocumentType DocumentType {
			get {
				for (int i = 0; i < ChildNodes.Count; i++) {
					XmlNode n = ChildNodes [i];
					if(n.NodeType == XmlNodeType.DocumentType)
						return (XmlDocumentType)n;
				}
				return null;
			}
		}

		public XmlImplementation Implementation {
			get { return implementation; }
		}

		public override string InnerXml {
			get {
				return base.InnerXml;
			}
			set {	// reason for overriding
				this.LoadXml (value);
			}
		}

		public override bool IsReadOnly {
			get { return false; }
		}

		internal bool IsStandalone {
			get {
				return FirstChild != null &&
					FirstChild.NodeType == XmlNodeType.XmlDeclaration &&
					((XmlDeclaration) this.FirstChild).Standalone == "yes";
			}
		}

		public override string LocalName {
			get { return "#document"; }
		}

		public override string Name {
			get { return "#document"; }
		}

		public XmlNameTable NameTable {
			get { return nameTable; }
		}

		public override XmlNodeType NodeType {
			get { return XmlNodeType.Document; }
		}

		internal override XPathNodeType XPathNodeType {
			get {
				return XPathNodeType.Root;
			}
		}

		public override XmlDocument OwnerDocument {
			get { return null; }
		}

		public bool PreserveWhitespace {
			get { return preserveWhitespace; }
			set { preserveWhitespace = value; }
		}

		internal XmlResolver Resolver {
			get { return resolver; }
		}

		internal override string XmlLang {
			get { return String.Empty; }
		}

		public virtual XmlResolver XmlResolver {
			set { resolver = value; }
		}

		internal override XmlSpace XmlSpace {
			get {
				return XmlSpace.None;
			}
		}
		
		internal Encoding TextEncoding {
			get {
				XmlDeclaration dec = FirstChild as XmlDeclaration;
			
				if (dec == null || dec.Encoding == "")
					return null;
				
				return Encoding.GetEncoding (dec.Encoding);
			}
		}

		#endregion

		#region Methods
		internal void AddIdenticalAttribute (XmlAttribute attr)
		{
			idTable [attr.Value] = attr;
		}

		public override XmlNode CloneNode (bool deep)
		{
			XmlDocument doc = implementation != null ? implementation.CreateDocument () : new XmlDocument ();
			doc.baseURI = baseURI;

			if(deep)
			{
				for (int i = 0; i < ChildNodes.Count; i++)
					doc.AppendChild (doc.ImportNode (ChildNodes [i], deep));
			}
			return doc;
		}

		public XmlAttribute CreateAttribute (string name)
		{
			string prefix;
			string localName;
			string namespaceURI = String.Empty;

			ParseName (name, out prefix, out localName);

			if (prefix == "xmlns" || (prefix == "" && localName == "xmlns"))
				namespaceURI = XmlNamespaceManager.XmlnsXmlns;
			else if (prefix == "xml")
				namespaceURI = XmlNamespaceManager.XmlnsXml;

			return CreateAttribute (prefix, localName, namespaceURI );
		}

		public XmlAttribute CreateAttribute (string qualifiedName, string namespaceURI)
		{
			string prefix;
			string localName;

			ParseName (qualifiedName, out prefix, out localName);

			return CreateAttribute (prefix, localName, namespaceURI);
		}

		public virtual XmlAttribute CreateAttribute (string prefix, string localName, string namespaceURI)
		{
			return CreateAttribute (prefix, localName, namespaceURI, false, true);
		}

		internal XmlAttribute CreateAttribute (string prefix, string localName, string namespaceURI, bool atomizedNames, bool checkNamespace)
		{
			if ((localName == null) || (localName == String.Empty))
				throw new ArgumentException ("The attribute local name cannot be empty.");

			return new XmlAttribute (prefix, localName, namespaceURI, this, atomizedNames, checkNamespace);
		}

		public virtual XmlCDataSection CreateCDataSection (string data)
		{
			return new XmlCDataSection (data, this);
		}

		public virtual XmlComment CreateComment (string data)
		{
			return new XmlComment (data, this);
		}

		protected internal virtual XmlAttribute CreateDefaultAttribute (string prefix, string localName, string namespaceURI)
		{
			XmlAttribute attr = CreateAttribute (prefix, localName, namespaceURI);
			attr.isDefault = true;
			return attr;
		}

		public virtual XmlDocumentFragment CreateDocumentFragment ()
		{
			return new XmlDocumentFragment (this);
		}

		public virtual XmlDocumentType CreateDocumentType (string name, string publicId,
								   string systemId, string internalSubset)
		{
			return new XmlDocumentType (name, publicId, systemId, internalSubset, this);
		}

		private XmlDocumentType CreateDocumentType (DTDObjectModel dtd)
		{
			return new XmlDocumentType (dtd, this);
		}

		public XmlElement CreateElement (string name)
		{
			return CreateElement (name, String.Empty);
		}

		public XmlElement CreateElement (
			string qualifiedName, 
			string namespaceURI)
		{
			string prefix;
			string localName;

			ParseName (qualifiedName, out prefix, out localName);
			
			return CreateElement (prefix, localName, namespaceURI);
		}

		public virtual XmlElement CreateElement (
			string prefix,
			string localName,
			string namespaceURI)
		{
			if ((localName == null) || (localName == String.Empty))
				throw new ArgumentException ("The local name for elements or attributes cannot be null or an empty string.");
			// FIXME: MS.NET has a weird behavior that they can Load() from XmlTextReader 
			// whose Namespaces = false, but their CreateElement() never allows qualified name.
			// I leave it as it is.
			if (!XmlChar.IsName (localName))
				throw new ArgumentException ("Invalid name.", "localName");
			return new XmlElement (prefix != null ? prefix : String.Empty, localName, namespaceURI != null ? namespaceURI : String.Empty, this, false);
		}

		public virtual XmlEntityReference CreateEntityReference (string name)
		{
			return new XmlEntityReference (name, this);
		}

		protected internal virtual XPathNavigator CreateNavigator (XmlNode node)
		{
			return new XmlDocumentNavigator (node);
		}

		public virtual XmlNode CreateNode (
			string nodeTypeString,
			string name,
			string namespaceURI)
		{
			return CreateNode (GetNodeTypeFromString (nodeTypeString), name, namespaceURI);
		}

		public virtual XmlNode CreateNode (
			XmlNodeType type,
			string name,
			string namespaceURI)
		{
			string prefix = null;
			string localName = name;

			if ((type == XmlNodeType.Attribute) || (type == XmlNodeType.Element) || (type == XmlNodeType.EntityReference))
				ParseName (name, out prefix, out localName);
			
			return CreateNode (type, prefix, localName, namespaceURI);
		}

		public virtual XmlNode CreateNode (
			XmlNodeType type,
			string prefix,
			string name,
			string namespaceURI)
		{
			switch (type) {
				case XmlNodeType.Attribute: return CreateAttribute (prefix, name, namespaceURI);
				case XmlNodeType.CDATA: return CreateCDataSection (null);
				case XmlNodeType.Comment: return CreateComment (null);
				case XmlNodeType.Document: return new XmlDocument ();
				case XmlNodeType.DocumentFragment: return CreateDocumentFragment ();
				case XmlNodeType.DocumentType: return CreateDocumentType (null, null, null, null);
				case XmlNodeType.Element: return CreateElement (prefix, name, namespaceURI);
				case XmlNodeType.EntityReference: return CreateEntityReference (null);
				case XmlNodeType.ProcessingInstruction: return CreateProcessingInstruction (null, null);
				case XmlNodeType.SignificantWhitespace: return CreateSignificantWhitespace (String.Empty);
				case XmlNodeType.Text: return CreateTextNode (null);
				case XmlNodeType.Whitespace: return CreateWhitespace (String.Empty);
				case XmlNodeType.XmlDeclaration: return CreateXmlDeclaration ("1.0", null, null);
				default: throw new ArgumentOutOfRangeException(String.Format("{0}\nParameter name: {1}",
							 "Specified argument was out of the range of valid values", type.ToString ()));
			}
		}

		public virtual XmlProcessingInstruction CreateProcessingInstruction (
			string target,
			string data)
		{
			return new XmlProcessingInstruction (target, data, this);
		}

		public virtual XmlSignificantWhitespace CreateSignificantWhitespace (string text)
		{
			if (!XmlChar.IsWhitespace (text))
				    throw new ArgumentException ("Invalid whitespace characters.");
			 
			return new XmlSignificantWhitespace (text, this);
		}

		public virtual XmlText CreateTextNode (string text)
		{
			return new XmlText (text, this);
		}

		public virtual XmlWhitespace CreateWhitespace (string text)
		{
			if (!XmlChar.IsWhitespace (text))
			    throw new ArgumentException ("Invalid whitespace characters.");
			 
			return new XmlWhitespace (text, this);
		}

		public virtual XmlDeclaration CreateXmlDeclaration (string version, string encoding,
								    string standalone)
		{
			if (version != "1.0")
				throw new ArgumentException ("version string is not correct.");

			if  ((standalone != null && standalone != String.Empty) && !((standalone == "yes") || (standalone == "no")))
				throw new ArgumentException ("standalone string is not correct.");

			return new XmlDeclaration (version, encoding, standalone, this);
		}

		// FIXME: Currently XmlAttributeCollection.SetNamedItem() does
		// add to the identity table, but in fact I delayed identity
		// check on GetIdenticalAttribute. To make such way complete,
		// we have to use MultiMap, not Hashtable.
		//
		// Well, MS.NET is also fragile around ID.
		public virtual XmlElement GetElementById (string elementId)
		{
			XmlAttribute attr = GetIdenticalAttribute (elementId);
			return attr != null ? attr.OwnerElement : null;
		}

		public virtual XmlNodeList GetElementsByTagName (string name)
		{
			ArrayList nodeArrayList = new ArrayList ();
			this.SearchDescendantElements (name, name == "*", nodeArrayList);
			return new XmlNodeArrayList (nodeArrayList);
		}

		public virtual XmlNodeList GetElementsByTagName (string localName, string namespaceURI)
		{
			ArrayList nodeArrayList = new ArrayList ();
			this.SearchDescendantElements (localName, localName == "*", namespaceURI, namespaceURI == "*", nodeArrayList);
			return new XmlNodeArrayList (nodeArrayList);
		}

		private XmlNodeType GetNodeTypeFromString (string nodeTypeString)
		{
			switch (nodeTypeString) {
				case "attribute": return XmlNodeType.Attribute;
				case "cdatasection": return XmlNodeType.CDATA;
				case "comment": return XmlNodeType.Comment;
				case "document": return XmlNodeType.Document;
				case "documentfragment": return XmlNodeType.DocumentFragment;
				case "documenttype": return XmlNodeType.DocumentType;
				case "element": return XmlNodeType.Element;
				case "entityreference": return XmlNodeType.EntityReference;
				case "processinginstruction": return XmlNodeType.ProcessingInstruction;
				case "significantwhitespace": return XmlNodeType.SignificantWhitespace;
				case "text": return XmlNodeType.Text;
				case "whitespace": return XmlNodeType.Whitespace;
				default:
					throw new ArgumentException(String.Format("The string doesn't represent any node type : {0}.", nodeTypeString));
			}
		}

		internal XmlAttribute GetIdenticalAttribute (string id)
		{
			XmlAttribute attr = this.idTable [id] as XmlAttribute;
			if (attr == null)
				return null;
			if (attr.OwnerElement == null || !attr.OwnerElement.IsRooted) {
//				idTable.Remove (id);
				return null;
			}
			return attr;
		}

		public virtual XmlNode ImportNode (XmlNode node, bool deep)
		{
			switch (node.NodeType) {
			case XmlNodeType.Attribute:
				XmlAttribute srcAtt = node as XmlAttribute;
				XmlAttribute dstAtt = this.CreateAttribute (srcAtt.Prefix, srcAtt.LocalName, srcAtt.NamespaceURI);
				for (int i = 0; i < srcAtt.ChildNodes.Count; i++)
					dstAtt.AppendChild (this.ImportNode (srcAtt.ChildNodes [i], deep));
				return dstAtt;

			case XmlNodeType.CDATA:
				return this.CreateCDataSection (node.Value);

			case XmlNodeType.Comment:
				return this.CreateComment (node.Value);

			case XmlNodeType.Document:
				throw new XmlException ("Document cannot be imported.");

			case XmlNodeType.DocumentFragment:
				XmlDocumentFragment df = this.CreateDocumentFragment ();
				if(deep)
					for (int i = 0; i < node.ChildNodes.Count; i++)
						df.AppendChild (this.ImportNode (node.ChildNodes [i], deep));
				return df;

			case XmlNodeType.DocumentType:
				throw new XmlException ("DocumentType cannot be imported.");

			case XmlNodeType.Element:
				XmlElement src = (XmlElement)node;
				XmlElement dst = this.CreateElement (src.Prefix, src.LocalName, src.NamespaceURI);
				for (int i = 0; i < src.Attributes.Count; i++) {
					XmlAttribute attr = src.Attributes [i];
					if(attr.Specified)	// copies only specified attributes
						dst.SetAttributeNode ((XmlAttribute) this.ImportNode (attr, deep));
				}
				if(deep)
					for (int i = 0; i < src.ChildNodes.Count; i++)
						dst.AppendChild (this.ImportNode (src.ChildNodes [i], deep));
				return dst;

			case XmlNodeType.EndElement:
				throw new XmlException ("Illegal ImportNode call for NodeType.EndElement");
			case XmlNodeType.EndEntity:
				throw new XmlException ("Illegal ImportNode call for NodeType.EndEntity");

			case XmlNodeType.EntityReference:
				return this.CreateEntityReference (node.Name);

			case XmlNodeType.None:
				throw new XmlException ("Illegal ImportNode call for NodeType.None");

			case XmlNodeType.ProcessingInstruction:
				XmlProcessingInstruction pi = node as XmlProcessingInstruction;
				return this.CreateProcessingInstruction (pi.Target, pi.Data);

			case XmlNodeType.SignificantWhitespace:
				return this.CreateSignificantWhitespace (node.Value);

			case XmlNodeType.Text:
				return this.CreateTextNode (node.Value);

			case XmlNodeType.Whitespace:
				return this.CreateWhitespace (node.Value);

			case XmlNodeType.XmlDeclaration:
				XmlDeclaration srcDecl = node as XmlDeclaration;
				return this.CreateXmlDeclaration (srcDecl.Version, srcDecl.Encoding, srcDecl.Standalone);

			default:
				throw new InvalidOperationException ("Cannot import specified node type: " + node.NodeType);
			}
		}

		public virtual void Load (Stream inStream)
		{
			XmlTextReader reader = new XmlTextReader (inStream);
			reader.XmlResolver = resolver;
			Load (reader);
		}

		public virtual void Load (string filename)
		{
			XmlTextReader xr = new XmlTextReader (filename);
			try {
				xr.XmlResolver = resolver;
				Load (xr);
			} finally {
				xr.Close ();
			}
		}

		public virtual void Load (TextReader txtReader)
		{
			XmlTextReader xr = new XmlTextReader (txtReader);
			xr.XmlResolver = resolver;
			Load (xr);
		}

		public virtual void Load (XmlReader xmlReader)
		{
			// Reset our document
			// For now this just means removing all our children but later this
			// may turn out o need to call a private method that resets other things
			// like properties we have, etc.
			RemoveAll ();

			this.baseURI = xmlReader.BaseURI;
			// create all contents with use of ReadNode()
			try {
				loadMode = true;
				do {
					XmlNode n = ReadNode (xmlReader);
					if (n == null)
						break;
					if (preserveWhitespace || n.NodeType != XmlNodeType.Whitespace)
						AppendChild (n);
				} while (true);
			} finally {
				loadMode = false;
			}
		}

		public virtual void LoadXml (string xml)
		{
			XmlTextReader xmlReader = new XmlTextReader (
				xml, XmlNodeType.Document, null);
			try {
				xmlReader.XmlResolver = resolver;
				Load (xmlReader);
			} finally {
				xmlReader.Close ();
			}
		}

		internal void onNodeChanged (XmlNode node, XmlNode Parent)
		{
			if (NodeChanged != null)
				NodeChanged (node, new XmlNodeChangedEventArgs
					(XmlNodeChangedAction.Change,
					node, Parent, Parent));
		}

		internal void onNodeChanging(XmlNode node, XmlNode Parent)
		{
			if (NodeChanging != null)
				NodeChanging (node, new XmlNodeChangedEventArgs
					(XmlNodeChangedAction.Change,
					node, Parent, Parent));
		}

		internal void onNodeInserted (XmlNode node, XmlNode newParent)
		{
			if (NodeInserted != null)
				NodeInserted (node, new XmlNodeChangedEventArgs
					(XmlNodeChangedAction.Insert,
					node, null, newParent));
		}

		internal void onNodeInserting (XmlNode node, XmlNode newParent)
		{
			if (NodeInserting != null)
				NodeInserting (node, new XmlNodeChangedEventArgs
					(XmlNodeChangedAction.Insert,
					node, null, newParent));
		}

		internal void onNodeRemoved (XmlNode node, XmlNode oldParent)
		{
			if (NodeRemoved != null)
				NodeRemoved (node, new XmlNodeChangedEventArgs
					(XmlNodeChangedAction.Remove,
					node, oldParent, null));
		}

		internal void onNodeRemoving (XmlNode node, XmlNode oldParent)
		{
			if (NodeRemoving != null)
				NodeRemoving (node, new XmlNodeChangedEventArgs
					(XmlNodeChangedAction.Remove,
					node, oldParent, null));
		}

		private void ParseName (string name, out string prefix, out string localName)
		{
			int indexOfColon = name.IndexOf (':');
			
			if (indexOfColon != -1) {
				prefix = name.Substring (0, indexOfColon);
				localName = name.Substring (indexOfColon + 1);
			} else {
				prefix = "";
				localName = name;
			}
		}

		// Reads XmlReader and creates Attribute Node.
		private XmlAttribute ReadAttributeNode(XmlReader reader)
		{
			if(reader.NodeType == XmlNodeType.Element)
				reader.MoveToFirstAttribute ();
			else if(reader.NodeType != XmlNodeType.Attribute)
				throw new InvalidOperationException (MakeReaderErrorMessage ("bad position to read attribute.", reader));
			XmlAttribute attribute = CreateAttribute (reader.Prefix, reader.LocalName, reader.NamespaceURI, false, false); // different NameTable
			ReadAttributeNodeValue (reader, attribute);

			// Keep the current reader position
			bool res;
			if (attribute.NamespaceURI == string.Empty || attribute.NamespaceURI == null)
				res = reader.MoveToAttribute (attribute.Name);
			else 
				res = reader.MoveToAttribute (attribute.LocalName, attribute.NamespaceURI);
			if (reader.IsDefault)
				attribute.SetDefault ();
			return attribute;
		}

		// Reads attribute from XmlReader and then creates attribute value children. XmlAttribute also uses this.
		internal void ReadAttributeNodeValue (XmlReader reader, XmlAttribute attribute)
		{
			while (reader.ReadAttributeValue ()) {
				if (reader.NodeType == XmlNodeType.EntityReference)
					attribute.AppendChild (CreateEntityReference (reader.Name));
				else
					// Children of Attribute is restricted to CharacterData and EntityReference (Comment is not allowed).
					attribute.AppendChild (CreateTextNode (reader.Value));
			}
		}

		public virtual XmlNode ReadNode (XmlReader reader)
		{
			switch (reader.ReadState) {
			case ReadState.Interactive:
				break;
			case ReadState.Initial:
				reader.Read ();
				break;
			default:
				return null;
			}

			XmlNode n;
			switch (reader.NodeType) {

			case XmlNodeType.Attribute:
				return ReadAttributeNode (reader);

			case XmlNodeType.CDATA:
				n = CreateCDataSection (reader.Value);
				break;

			case XmlNodeType.Comment:
				n = CreateComment (reader.Value);
				break;

			case XmlNodeType.Element:
				XmlElement element = CreateElement (reader.Prefix, reader.LocalName, reader.NamespaceURI);
				element.IsEmpty = reader.IsEmptyElement;

				// set the element's attributes.
				if (reader.MoveToFirstAttribute ()) {
					do {
						element.SetAttributeNode (ReadAttributeNode (reader));
					} while (reader.MoveToNextAttribute ());
					reader.MoveToElement ();
				}

				int depth = reader.Depth;

				if (element.IsEmpty) {
					n = element;
					break;
				}

				reader.Read ();
				while (reader.Depth > depth) {
					n = ReadNode (reader);
					if (preserveWhitespace || n.NodeType != XmlNodeType.Whitespace)
						element.AppendChild (n);
				}
				n = element;
				break;

			case XmlNodeType.ProcessingInstruction:
				n = CreateProcessingInstruction (reader.Name, reader.Value);
				break;

			case XmlNodeType.Text:
				n = CreateTextNode (reader.Value);
				break;

			case XmlNodeType.XmlDeclaration:
				n = CreateXmlDeclaration ("1.0" , String.Empty, String.Empty);
				n.Value = reader.Value;
				break;

			case XmlNodeType.DocumentType:
				DTDObjectModel dtd = null;
				XmlTextReader xtReader = reader as XmlTextReader;
				if (xtReader != null)
					dtd = xtReader.DTD;
				XmlNodeReader xnReader = reader as XmlNodeReader;
				if (xnReader != null)
					dtd = xnReader.GetInternalParserContext ().Dtd;
				XmlValidatingReader xvReader = reader as XmlValidatingReader;
				if (xvReader != null)
					dtd = xvReader.GetInternalParserContext ().Dtd;
				IHasXmlParserContext ctxReader = reader as IHasXmlParserContext;
				if (ctxReader != null)
					dtd = ctxReader.ParserContext.Dtd;

				if (dtd != null)
					n = CreateDocumentType (dtd);
				else
					n = CreateDocumentType (reader.Name, reader ["PUBLIC"], reader ["SYSTEM"], reader.Value);
				break;

			case XmlNodeType.EntityReference:
				if (this.loadMode && this.DocumentType != null &&
					DocumentType.Entities.GetNamedItem (reader.Name) == null)
					throw new XmlException ("Reference to undeclared entity was found.");

				n = CreateEntityReference (reader.Name);
				break;

			case XmlNodeType.SignificantWhitespace:
				n = CreateSignificantWhitespace (reader.Value);
				break;

			case XmlNodeType.Whitespace:
				n = CreateWhitespace (reader.Value);
				break;

			case XmlNodeType.None:
				return null;

			default:
				// No idea why MS does throw NullReferenceException ;-P
				throw new NullReferenceException ("Unexpected node type " + reader.NodeType + ".");
			}

			reader.Read ();
			return n;
		}

		private string MakeReaderErrorMessage (string message, XmlReader reader)
		{
			IXmlLineInfo li = reader as IXmlLineInfo;
			if (li != null)
				return String.Format ("{0} Line number = {1}, Inline position = {2}.", message, li.LineNumber, li.LinePosition);
			else
				return message;
		}

		internal void RemoveIdenticalAttribute (string id)
		{
			idTable.Remove (id);
		}

		public virtual void Save(Stream outStream)
		{
			XmlTextWriter xmlWriter = new XmlTextWriter (outStream, TextEncoding);
			xmlWriter.Formatting = Formatting.Indented;
			WriteContentTo (xmlWriter);
			xmlWriter.Flush ();
		}

		public virtual void Save (string filename)
		{
			XmlTextWriter xmlWriter = new XmlTextWriter (filename, TextEncoding);
			try {
				xmlWriter.Formatting = Formatting.Indented;
				WriteContentTo (xmlWriter);
			} finally {
				xmlWriter.Close ();
			}
		}

		public virtual void Save (TextWriter writer)
		{
			XmlTextWriter xmlWriter = new XmlTextWriter (writer);
			xmlWriter.Formatting = Formatting.Indented;
			WriteContentTo (xmlWriter);
			xmlWriter.Flush ();
		}

		public virtual void Save (XmlWriter xmlWriter)
		{
			//
			// This should preserve white space if PreserveWhiteSpace is true
			//
			bool autoXmlDecl = FirstChild != null && FirstChild.NodeType != XmlNodeType.XmlDeclaration;
			if (autoXmlDecl)
				xmlWriter.WriteStartDocument ();
			WriteContentTo (xmlWriter);
			if (autoXmlDecl)
				xmlWriter.WriteEndDocument ();
			xmlWriter.Flush ();
		}

		public override void WriteContentTo (XmlWriter w)
		{
			for (int i = 0; i < ChildNodes.Count; i++)
				ChildNodes [i].WriteTo (w);
		}

		public override void WriteTo (XmlWriter w)
		{
			WriteContentTo (w);
		}

		private void AddDefaultNameTableKeys ()
		{
			// The following keys are default of MS .NET Framework
			nameTable.Add ("#text");
			nameTable.Add ("xml");
			nameTable.Add ("xmlns");
			nameTable.Add ("#entity");
			nameTable.Add ("#document-fragment");
			nameTable.Add ("#comment");
			nameTable.Add ("space");
			nameTable.Add ("id");
			nameTable.Add ("#whitespace");
			nameTable.Add ("http://www.w3.org/2000/xmlns/");
			nameTable.Add ("#cdata-section");
			nameTable.Add ("lang");
			nameTable.Add ("#document");
			nameTable.Add ("#significant-whitespace");
		}
		#endregion
	}
}