mcs/class/System.Xml.Linq/System.Xml.Linq/XElement.cs

   1 //
   2 // Authors:
   3 //   Atsushi Enomoto
   4 //
   5 // Copyright 2007 Novell (http://www.novell.com)
   6 //
   7 // Permission is hereby granted, free of charge, to any person obtaining
   8 // a copy of this software and associated documentation files (the
   9 // "Software"), to deal in the Software without restriction, including
  10 // without limitation the rights to use, copy, modify, merge, publish,
  11 // distribute, sublicense, and/or sell copies of the Software, and to
  12 // permit persons to whom the Software is furnished to do so, subject to
  13 // the following conditions:
  14 //
  15 // The above copyright notice and this permission notice shall be
  16 // included in all copies or substantial portions of the Software.
  17 //
  18 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  19 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  20 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  21 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  22 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  23 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  24 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25 //
  26
  27 using System;
  28 using System.Collections;
  29 using System.Collections.Generic;
  30 using System.IO;
  31 using System.Linq;
  32 using System.Text;
  33 using System.Xml;
  34 using System.Xml.Schema;
  35 using System.Xml.Serialization;
  36
  37 namespace System.Xml.Linq
  38 {
  39         [XmlSchemaProvider (null, IsAny = true)]
  40         public class XElement : XContainer, IXmlSerializable
  41         {
  42                 static IEnumerable <XElement> emptySequence =
  43                         new List <XElement> ();
  44
  45                 public static IEnumerable <XElement> EmptySequence {
  46                         get { return emptySequence; }
  47                 }
  48
  49                 XName name;
  50                 XAttribute attr_first, attr_last;
  51                 bool explicit_is_empty = true;
  52
  53                 public XElement (XName name, object content)
  54                 {
  55                         if (name == null)
  56                                 throw new ArgumentNullException ("name");
  57                         this.name = name;
  58                         Add (content);
  59                 }
  60
  61                 public XElement (XElement other)
  62                 {
  63                         if (other == null)
  64                                 throw new ArgumentNullException ("other");
  65                         name = other.name;
  66                         Add (other.Attributes ());
  67                         Add (other.Nodes ());
  68                 }
  69
  70                 public XElement (XName name)
  71                 {
  72                         if (name == null)
  73                                 throw new ArgumentNullException ("name");
  74                         this.name = name;
  75                 }
  76
  77                 public XElement (XName name, params object [] content)
  78                 {
  79                         if (name == null)
  80                                 throw new ArgumentNullException ("name");
  81                         this.name = name;
  82                         Add (content);
  83                 }
  84
  85                 public XElement (XStreamingElement other)
  86                 {
  87                         if (other == null)
  88                                 throw new ArgumentNullException ("other");
  89                         this.name = other.Name;
  90                         Add (other.Contents);
  91                 }
  92
  93                 [CLSCompliant (false)]
  94                 public static explicit operator bool (XElement element)
  95                 {
  96                         if (element == null)
  97                                 throw new ArgumentNullException ("element");
  98                         return XUtil.ConvertToBoolean (element.Value);
  99                 }
 100
 101                 [CLSCompliant (false)]
 102                 public static explicit operator bool? (XElement element)
 103                 {
 104                         if (element == null)
 105                                 return null;
 106
 107                         return element.Value == null ? (bool?) null : XUtil.ConvertToBoolean (element.Value);
 108                 }
 109
 110                 [CLSCompliant (false)]
 111                 public static explicit operator DateTime (XElement element)
 112                 {
 113                         if (element == null)
 114                                 throw new ArgumentNullException ("element");
 115                         return XUtil.ToDateTime (element.Value);
 116                 }
 117
 118                 [CLSCompliant (false)]
 119                 public static explicit operator DateTime? (XElement element)
 120                 {
 121                         if (element == null)
 122                                 return null;
 123
 124                         return element.Value == null ? (DateTime?) null : XUtil.ToDateTime (element.Value);
 125                 }
 126
 127 #if !TARGET_JVM // Same as for System.Xml.XmlConvert.ToDateTimeOffset
 128
 129                 [CLSCompliant (false)]
 130                 public static explicit operator DateTimeOffset (XElement element)
 131                 {
 132                         if (element == null)
 133                                 throw new ArgumentNullException ("element");
 134                         return XmlConvert.ToDateTimeOffset (element.Value);
 135                 }
 136
 137                 [CLSCompliant (false)]
 138                 public static explicit operator DateTimeOffset? (XElement element)
 139                 {
 140                         if (element == null)
 141                                 return null;
 142
 143                         return element.Value == null ? (DateTimeOffset?) null : XmlConvert.ToDateTimeOffset (element.Value);
 144                 }
 145
 146 #endif
 147
 148                 [CLSCompliant (false)]
 149                 public static explicit operator decimal (XElement element)
 150                 {
 151                         if (element == null)
 152                                 throw new ArgumentNullException ("element");
 153                         return XmlConvert.ToDecimal (element.Value);
 154                 }
 155
 156                 [CLSCompliant (false)]
 157                 public static explicit operator decimal? (XElement element)
 158                 {
 159                         if (element == null)
 160                                 return null;
 161
 162                         return element.Value == null ? (decimal?) null : XmlConvert.ToDecimal (element.Value);
 163                 }
 164
 165                 [CLSCompliant (false)]
 166                 public static explicit operator double (XElement element)
 167                 {
 168                         if (element == null)
 169                                 throw new ArgumentNullException ("element");
 170                         return XmlConvert.ToDouble (element.Value);
 171                 }
 172
 173                 [CLSCompliant (false)]
 174                 public static explicit operator double? (XElement element)
 175                 {
 176                         if (element == null)
 177                                 return null;
 178
 179                         return element.Value == null ? (double?) null : XmlConvert.ToDouble (element.Value);
 180                 }
 181
 182                 [CLSCompliant (false)]
 183                 public static explicit operator float (XElement element)
 184                 {
 185                         if (element == null)
 186                                 throw new ArgumentNullException ("element");
 187                         return XmlConvert.ToSingle (element.Value);
 188                 }
 189
 190                 [CLSCompliant (false)]
 191                 public static explicit operator float? (XElement element)
 192                 {
 193                         if (element == null)
 194                                 return null;
 195
 196                         return element.Value == null ? (float?) null : XmlConvert.ToSingle (element.Value);
 197                 }
 198
 199                 [CLSCompliant (false)]
 200                 public static explicit operator Guid (XElement element)
 201                 {
 202                         if (element == null)
 203                                 throw new ArgumentNullException ("element");
 204                         return XmlConvert.ToGuid (element.Value);
 205                 }
 206
 207                 [CLSCompliant (false)]
 208                 public static explicit operator Guid? (XElement element)
 209                 {
 210                         if (element == null)
 211                                 return null;
 212
 213                         return element.Value == null ? (Guid?) null : XmlConvert.ToGuid (element.Value);
 214                 }
 215
 216                 [CLSCompliant (false)]
 217                 public static explicit operator int (XElement element)
 218                 {
 219                         if (element == null)
 220                                 throw new ArgumentNullException ("element");
 221                         return XmlConvert.ToInt32 (element.Value);
 222                 }
 223
 224                 [CLSCompliant (false)]
 225                 public static explicit operator int? (XElement element)
 226                 {
 227                         if (element == null)
 228                                 return null;
 229
 230                         return element.Value == null ? (int?) null : XmlConvert.ToInt32 (element.Value);
 231                 }
 232
 233                 [CLSCompliant (false)]
 234                 public static explicit operator long (XElement element)
 235                 {
 236                         if (element == null)
 237                                 throw new ArgumentNullException ("element");
 238                         return XmlConvert.ToInt64 (element.Value);
 239                 }
 240
 241                 [CLSCompliant (false)]
 242                 public static explicit operator long? (XElement element)
 243                 {
 244                         if (element == null)
 245                                 return null;
 246
 247                         return element.Value == null ? (long?) null : XmlConvert.ToInt64 (element.Value);
 248                 }
 249
 250                 [CLSCompliant (false)]
 251                 public static explicit operator uint (XElement element)
 252                 {
 253                         if (element == null)
 254                                 throw new ArgumentNullException ("element");
 255                         return XmlConvert.ToUInt32 (element.Value);
 256                 }
 257
 258                 [CLSCompliant (false)]
 259                 public static explicit operator uint? (XElement element)
 260                 {
 261                         if (element == null)
 262                                 return null;
 263
 264                         return element.Value == null ? (uint?) null : XmlConvert.ToUInt32 (element.Value);
 265                 }
 266
 267                 [CLSCompliant (false)]
 268                 public static explicit operator ulong (XElement element)
 269                 {
 270                         if (element == null)
 271                                 throw new ArgumentNullException ("element");
 272                         return XmlConvert.ToUInt64 (element.Value);
 273                 }
 274
 275                 [CLSCompliant (false)]
 276                 public static explicit operator ulong? (XElement element)
 277                 {
 278                         if (element == null)
 279                                 return null;
 280
 281                         return element.Value == null ? (ulong?) null : XmlConvert.ToUInt64 (element.Value);
 282                 }
 283
 284                 [CLSCompliant (false)]
 285                 public static explicit operator TimeSpan (XElement element)
 286                 {
 287                         if (element == null)
 288                                 throw new ArgumentNullException ("element");
 289                         return XmlConvert.ToTimeSpan (element.Value);
 290                 }
 291
 292                 [CLSCompliant (false)]
 293                 public static explicit operator TimeSpan? (XElement element)
 294                 {
 295                         if (element == null)
 296                                 return null;
 297
 298                         return element.Value == null ? (TimeSpan?) null : XmlConvert.ToTimeSpan (element.Value);
 299                 }
 300
 301                 [CLSCompliant (false)]
 302                 public static explicit operator string (XElement element)
 303                 {
 304                         if (element == null)
 305                                 return null;
 306
 307                         return element.Value;
 308                 }
 309
 310                 public XAttribute FirstAttribute {
 311                         get { return attr_first; }
 312                         internal set { attr_first = value; }
 313                 }
 314
 315                 public XAttribute LastAttribute {
 316                         get { return attr_last; }
 317                         internal set { attr_last = value; }
 318                 }
 319
 320                 public bool HasAttributes {
 321                         get { return attr_first != null; }
 322                 }
 323
 324                 public bool HasElements {
 325                         get {
 326                                 foreach (object o in Nodes ())
 327                                         if (o is XElement)
 328                                                 return true;
 329                                 return false;
 330                         }
 331                 }
 332
 333                 public bool IsEmpty {
 334                         get { return !Nodes ().GetEnumerator ().MoveNext () && explicit_is_empty; }
 335                         internal set { explicit_is_empty = value; }
 336                 }
 337
 338                 public XName Name {
 339                         get { return name; }
 340                         set {
 341                                 if (value == null)
 342                                         throw new ArgumentNullException ("Name");
 343                                 OnNameChanging (this);
 344                                 name = value;
 345                                 OnNameChanged (this);
 346                         }
 347                 }
 348
 349                 public override XmlNodeType NodeType {
 350                         get { return XmlNodeType.Element; }
 351                 }
 352
 353                 public string Value {
 354                         get {
 355                                 StringBuilder sb = null;
 356                                 foreach (XNode n in Nodes ()) {
 357                                         if (sb == null)
 358                                                 sb = new StringBuilder ();
 359                                         if (n is XText)
 360                                                 sb.Append (((XText) n).Value);
 361                                         else if (n is XElement)
 362                                                 sb.Append (((XElement) n).Value);
 363                                 }
 364                                 return sb == null ? String.Empty : sb.ToString ();
 365                         }
 366                         set {
 367                                 RemoveNodes ();
 368                                 Add (value);
 369                         }
 370                 }
 371
 372                 IEnumerable <XElement> GetAncestorList (XName name, bool getMeIn)
 373                 {
 374                         List <XElement> list = new List <XElement> ();
 375                         if (getMeIn)
 376                                 list.Add (this);
 377                         for (XElement el = Parent as XElement; el != null; el = el.Parent as XElement)
 378                                 if (name == null || el.Name == name)
 379                                         list.Add (el);
 380                         return list;
 381                 }
 382
 383                 public XAttribute Attribute (XName name)
 384                 {
 385                         foreach (XAttribute a in Attributes ())
 386                                 if (a.Name == name)
 387                                         return a;
 388                         return null;
 389                 }
 390
 391                 public IEnumerable <XAttribute> Attributes ()
 392                 {
 393                         XAttribute next;
 394                         for (XAttribute a = attr_first; a != null; a = next) {
 395                                 next = a.NextAttribute;
 396                                 yield return a;
 397                         }
 398                 }
 399
 400                 // huh?
 401                 public IEnumerable <XAttribute> Attributes (XName name)
 402                 {
 403                         foreach (XAttribute a in Attributes ())
 404                                 if (a.Name == name)
 405                                         yield return a;
 406                 }
 407
 408                 static void DefineDefaultSettings (XmlReaderSettings settings, LoadOptions options)
 409                 {
 410                         settings.ProhibitDtd = false;
 411
 412                         settings.IgnoreWhitespace = (options & LoadOptions.PreserveWhitespace) == 0;
 413                 }
 414
 415                 static XmlReaderSettings CreateDefaultSettings (LoadOptions options)
 416                 {
 417                         var settings = new XmlReaderSettings ();
 418                         DefineDefaultSettings (settings, options);
 419                         return settings;
 420                 }
 421
 422                 public static XElement Load (string uri)
 423                 {
 424                         return Load (uri, LoadOptions.None);
 425                 }
 426
 427                 public static XElement Load (string uri, LoadOptions options)
 428                 {
 429                         XmlReaderSettings s = CreateDefaultSettings (options);
 430
 431                         using (XmlReader r = XmlReader.Create (uri, s)) {
 432                                 return LoadCore (r, options);
 433                         }
 434                 }
 435
 436                 public static XElement Load (TextReader textReader)
 437                 {
 438                         return Load (textReader, LoadOptions.None);
 439                 }
 440
 441                 public static XElement Load (TextReader textReader, LoadOptions options)
 442                 {
 443                         XmlReaderSettings s = CreateDefaultSettings (options);
 444
 445                         using (XmlReader r = XmlReader.Create (textReader, s)) {
 446                                 return LoadCore (r, options);
 447                         }
 448                 }
 449
 450                 public static XElement Load (XmlReader reader)
 451                 {
 452                         return Load (reader, LoadOptions.None);
 453                 }
 454
 455                 public static XElement Load (XmlReader reader, LoadOptions options)
 456                 {
 457                         XmlReaderSettings s = reader.Settings != null ? reader.Settings.Clone () : new XmlReaderSettings ();
 458                         DefineDefaultSettings (s, options);
 459
 460                         using (XmlReader r = XmlReader.Create (reader, s)) {
 461                                 return LoadCore (r, options);
 462                         }
 463                 }
 464
 465 #if MOBILE || NET_4_0
 466                 public static XElement Load (Stream stream)
 467                 {
 468                         return Load (stream, LoadOptions.None);
 469                 }
 470
 471                 public static XElement Load (Stream stream, LoadOptions options)
 472                 {
 473                         XmlReaderSettings s = new XmlReaderSettings ();
 474                         DefineDefaultSettings (s, options);
 475
 476                         using (XmlReader r = XmlReader.Create (stream, s)) {
 477                                 return LoadCore (r, options);
 478                         }
 479                 }
 480 #endif
 481
 482                 internal static XElement LoadCore (XmlReader r, LoadOptions options)
 483                 {
 484                         r.MoveToContent ();
 485                         if (r.NodeType != XmlNodeType.Element)
 486                                 throw new InvalidOperationException ("The XmlReader must be positioned at an element");
 487                         XName name = XName.Get (r.LocalName, r.NamespaceURI);
 488                         XElement e = new XElement (name);
 489                         e.FillLineInfoAndBaseUri (r, options);
 490
 491                         if (r.MoveToFirstAttribute ()) {
 492                                 do {
 493                                         // not sure how current Orcas behavior makes sense here though ...
 494                                         if (r.LocalName == "xmlns" && r.NamespaceURI == XNamespace.Xmlns.NamespaceName)
 495                                                 e.SetAttributeValue (XNamespace.None.GetName ("xmlns"), r.Value);
 496                                         else
 497                                                 e.SetAttributeValue (XName.Get (r.LocalName, r.NamespaceURI), r.Value);
 498                                         e.LastAttribute.FillLineInfoAndBaseUri (r, options);
 499                                 } while (r.MoveToNextAttribute ());
 500                                 r.MoveToElement ();
 501                         }
 502                         if (!r.IsEmptyElement) {
 503                                 r.Read ();
 504                                 e.ReadContentFrom (r, options);
 505                                 r.ReadEndElement ();
 506                                 e.explicit_is_empty = false;
 507                         } else {
 508                                 e.explicit_is_empty = true;
 509                                 r.Read ();
 510                         }
 511                         return e;
 512                 }
 513
 514                 public static XElement Parse (string text)
 515                 {
 516                         return Parse (text, LoadOptions.None);
 517                 }
 518
 519                 public static XElement Parse (string text, LoadOptions options)
 520                 {
 521                         return Load (new StringReader (text), options);
 522                 }
 523
 524                 public void RemoveAll ()
 525                 {
 526                         RemoveAttributes ();
 527                         RemoveNodes ();
 528                 }
 529
 530                 public void RemoveAttributes ()
 531                 {
 532                         while (attr_first != null)
 533                                 attr_last.Remove ();
 534                 }
 535
 536                 public void Save (string fileName)
 537                 {
 538                         Save (fileName, SaveOptions.None);
 539                 }
 540
 541                 public void Save (string fileName, SaveOptions options)
 542                 {
 543                         XmlWriterSettings s = new XmlWriterSettings ();
 544
 545                         if ((options & SaveOptions.DisableFormatting) == SaveOptions.None)
 546                                 s.Indent = true;
 547 #if NET_4_0 || MOBILE
 548                         if ((options & SaveOptions.OmitDuplicateNamespaces) == SaveOptions.OmitDuplicateNamespaces)
 549                                 s.NamespaceHandling |= NamespaceHandling.OmitDuplicates;
 550 #endif
 551                         using (XmlWriter w = XmlWriter.Create (fileName, s)) {
 552                                 Save (w);
 553                         }
 554                 }
 555
 556                 public void Save (TextWriter textWriter)
 557                 {
 558                         Save (textWriter, SaveOptions.None);
 559                 }
 560
 561                 public void Save (TextWriter textWriter, SaveOptions options)
 562                 {
 563                         XmlWriterSettings s = new XmlWriterSettings ();
 564
 565                         if ((options & SaveOptions.DisableFormatting) == SaveOptions.None)
 566                                 s.Indent = true;
 567 #if NET_4_0 || MOBILE
 568                         if ((options & SaveOptions.OmitDuplicateNamespaces) == SaveOptions.OmitDuplicateNamespaces)
 569                                 s.NamespaceHandling |= NamespaceHandling.OmitDuplicates;
 570 #endif
 571                         using (XmlWriter w = XmlWriter.Create (textWriter, s)) {
 572                                 Save (w);
 573                         }
 574                 }
 575
 576                 public void Save (XmlWriter writer)
 577                 {
 578                         WriteTo (writer);
 579                 }
 580
 581 #if NET_4_0 || MOBILE
 582                 public void Save (Stream stream)
 583                 {
 584                         Save (stream, SaveOptions.None);
 585                 }
 586
 587                 public void Save (Stream stream, SaveOptions options)
 588                 {
 589                         XmlWriterSettings s = new XmlWriterSettings ();
 590                         if ((options & SaveOptions.DisableFormatting) == SaveOptions.None)
 591                                 s.Indent = true;
 592                         if ((options & SaveOptions.OmitDuplicateNamespaces) == SaveOptions.OmitDuplicateNamespaces)
 593                                 s.NamespaceHandling |= NamespaceHandling.OmitDuplicates;
 594
 595                         using (var writer = XmlWriter.Create (stream, s)){
 596                                 Save (writer);
 597                         }
 598                 }
 599 #endif
 600                 public IEnumerable <XElement> AncestorsAndSelf ()
 601                 {
 602                         return GetAncestorList (null, true);
 603                 }
 604
 605                 public IEnumerable <XElement> AncestorsAndSelf (XName name)
 606                 {
 607                         return GetAncestorList (name, true);
 608                 }
 609
 610                 public IEnumerable <XElement> DescendantsAndSelf ()
 611                 {
 612                         List <XElement> list = new List <XElement> ();
 613                         list.Add (this);
 614                         list.AddRange (Descendants ());
 615                         return list;
 616                 }
 617
 618                 public IEnumerable <XElement> DescendantsAndSelf (XName name)
 619                 {
 620                         List <XElement> list = new List <XElement> ();
 621                         if (name == this.name)
 622                                 list.Add (this);
 623                         list.AddRange (Descendants (name));
 624                         return list;
 625                 }
 626
 627                 public IEnumerable <XNode> DescendantNodesAndSelf ()
 628                 {
 629                         yield return this;
 630                         foreach (XNode node in DescendantNodes ())
 631                                 yield return node;
 632                 }
 633
 634                 public void SetAttributeValue (XName name, object value)
 635                 {
 636                         XAttribute a = Attribute (name);
 637                         if (value == null) {
 638                                 if (a != null)
 639                                         a.Remove ();
 640                         } else {
 641                                 if (a == null) {
 642                                         SetAttributeObject (new XAttribute (name, value));
 643                                 }
 644                                 else
 645                                         a.Value = XUtil.ToString (value);
 646                         }
 647                 }
 648
 649                 void SetAttributeObject (XAttribute a)
 650                 {
 651                         OnAddingObject (a);
 652                         a = (XAttribute) XUtil.GetDetachedObject (a);
 653                         a.SetOwner (this);
 654                         if (attr_first == null) {
 655                                 attr_first = a;
 656                                 attr_last = a;
 657                         } else {
 658                                 attr_last.NextAttribute = a;
 659                                 a.PreviousAttribute = attr_last;
 660                                 attr_last = a;
 661                         }
 662                         OnAddedObject (a);
 663                 }
 664
 665                 string LookupPrefix (string ns, XmlWriter w)
 666                 {
 667                         string prefix = ns.Length > 0 ? GetPrefixOfNamespace (ns) ?? w.LookupPrefix (ns) : String.Empty;
 668                         foreach (XAttribute a in Attributes ()) {
 669                                 if (a.IsNamespaceDeclaration && a.Value == ns) {
 670                                         if (a.Name.Namespace == XNamespace.Xmlns)
 671                                                 prefix = a.Name.LocalName;
 672                                         // otherwise xmlns="..."
 673                                         break;
 674                                 }
 675                         }
 676                         return prefix;
 677                 }
 678
 679                 static string CreateDummyNamespace (ref int createdNS, IEnumerable<XAttribute> atts, bool isAttr)
 680                 {
 681                         if (!isAttr && atts.All (a => a.Name.LocalName != "xmlns" || a.Name.NamespaceName == XNamespace.Xmlns.NamespaceName))
 682                                 return String.Empty;
 683                         string p = null;
 684                         do {
 685                                 p = "p" + (++createdNS);
 686                                 // check conflict
 687                                 if (atts.All (a => a.Name.LocalName != p || a.Name.NamespaceName == XNamespace.Xmlns.NamespaceName))
 688                                         break;
 689                         } while (true);
 690                         return p;
 691                 }
 692
 693                 public override void WriteTo (XmlWriter writer)
 694                 {
 695                         // some people expect the same prefix output as in input,
 696                         // in the loss of performance... see bug #466423.
 697                         string prefix = LookupPrefix (name.NamespaceName, writer);
 698                         int createdNS = 0;
 699                         if (prefix == null)
 700                                 prefix = CreateDummyNamespace (ref createdNS, Attributes (), false);
 701
 702                         writer.WriteStartElement (prefix, name.LocalName, name.Namespace.NamespaceName);
 703
 704                         foreach (XAttribute a in Attributes ()) {
 705                                 if (a.IsNamespaceDeclaration) {
 706                                         if (a.Name.Namespace == XNamespace.Xmlns)
 707                                                 writer.WriteAttributeString ("xmlns", a.Name.LocalName, XNamespace.Xmlns.NamespaceName, a.Value);
 708                                         else
 709                                                 writer.WriteAttributeString ("xmlns", a.Value);
 710                                 } else {
 711                                         string apfix = LookupPrefix (a.Name.NamespaceName, writer);
 712                                         if (apfix == null)
 713                                                 apfix = CreateDummyNamespace (ref createdNS, Attributes (), true);
 714                                         writer.WriteAttributeString (apfix, a.Name.LocalName, a.Name.Namespace.NamespaceName, a.Value);
 715                                 }
 716                         }
 717
 718                         foreach (XNode node in Nodes ())
 719                                 node.WriteTo (writer);
 720
 721                         if (explicit_is_empty)
 722                                 writer.WriteEndElement ();
 723                         else
 724                                 writer.WriteFullEndElement ();
 725                 }
 726
 727                 public XNamespace GetDefaultNamespace ()
 728                 {
 729                         for (XElement el = this; el != null; el = el.Parent)
 730                                 foreach (XAttribute a in el.Attributes ())
 731                                         if (a.IsNamespaceDeclaration && a.Name.Namespace == XNamespace.None)
 732                                                 return XNamespace.Get (a.Value);
 733                         return XNamespace.None; // nothing is declared.
 734                 }
 735
 736                 public XNamespace GetNamespaceOfPrefix (string prefix)
 737                 {
 738                         for (XElement el = this; el != null; el = el.Parent)
 739                                 foreach (XAttribute a in el.Attributes ())
 740                                         if (a.IsNamespaceDeclaration && (prefix.Length == 0 && a.Name.LocalName == "xmlns" || a.Name.LocalName == prefix))
 741                                                 return XNamespace.Get (a.Value);
 742                         return XNamespace.None; // nothing is declared.
 743                 }
 744
 745                 public string GetPrefixOfNamespace (XNamespace ns)
 746                 {
 747                         foreach (string prefix in GetPrefixOfNamespaceCore (ns))
 748                                 if (GetNamespaceOfPrefix (prefix) == ns)
 749                                         return prefix;
 750                         return null; // nothing is declared
 751                 }
 752
 753                 IEnumerable<string> GetPrefixOfNamespaceCore (XNamespace ns)
 754                 {
 755                         for (XElement el = this; el != null; el = el.Parent)
 756                                 foreach (XAttribute a in el.Attributes ())
 757                                         if (a.IsNamespaceDeclaration && a.Value == ns.NamespaceName)
 758                                                 yield return a.Name.Namespace == XNamespace.None ? String.Empty : a.Name.LocalName;
 759                 }
 760
 761                 public void ReplaceAll (object content)
 762                 {
 763                         RemoveNodes ();
 764                         Add (content);
 765                 }
 766
 767                 public void ReplaceAll (params object [] content)
 768                 {
 769                         RemoveNodes ();
 770                         Add (content);
 771                 }
 772
 773                 public void ReplaceAttributes (object content)
 774                 {
 775                         RemoveAttributes ();
 776                         Add (content);
 777                 }
 778
 779                 public void ReplaceAttributes (params object [] content)
 780                 {
 781                         RemoveAttributes ();
 782                         Add (content);
 783                 }
 784
 785                 public void SetElementValue (XName name, object value)
 786                 {
 787                         var element = Element (name);
 788                         if (element == null && value != null) {
 789                                 Add (new XElement (name, value));
 790                         } else if (element != null && value == null) {
 791                                 element.Remove ();
 792                         } else
 793                                 element.SetValue (value);
 794                 }
 795
 796                 public void SetValue (object value)
 797                 {
 798                         if (value == null)
 799                                 throw new ArgumentNullException ("value");
 800                         if (value is XAttribute || value is XDocument || value is XDeclaration || value is XDocumentType)
 801                                 throw new ArgumentException (String.Format ("Node type {0} is not allowed as element value", value.GetType ()));
 802                         RemoveNodes ();
 803                         foreach (object o in XUtil.ExpandArray (value))
 804                                 Add (o);
 805                 }
 806
 807                 internal override bool OnAddingObject (object o, bool rejectAttribute, XNode refNode, bool addFirst)
 808                 {
 809                         if (o is XDocument || o is XDocumentType || o is XDeclaration || (rejectAttribute && o is XAttribute))
 810                                 throw new ArgumentException (String.Format ("A node of type {0} cannot be added as a content", o.GetType ()));
 811
 812                         XAttribute a = o as XAttribute;
 813                         if (a != null) {
 814                                 foreach (XAttribute ia in Attributes ())
 815                                         if (a.Name == ia.Name)
 816                                                 throw new InvalidOperationException (String.Format ("Duplicate attribute: {0}", a.Name));
 817                                 SetAttributeObject (a);
 818                                 return true;
 819                         }
 820                         else if (o is string && refNode is XText) {
 821                                 ((XText) refNode).Value += o as string;
 822                                 return true;
 823                         }
 824                         else
 825                                 return false;
 826                 }
 827
 828                 void IXmlSerializable.WriteXml (XmlWriter writer)
 829                 {
 830                         Save (writer);
 831                 }
 832
 833                 void IXmlSerializable.ReadXml (XmlReader reader)
 834                 {
 835                         ReadContentFrom (reader, LoadOptions.None);
 836                 }
 837
 838                 XmlSchema IXmlSerializable.GetSchema ()
 839                 {
 840                         return null;
 841                 }
 842         }
 843 }