mcs/class/System.XML/System.Xml/XmlWriter.cs

   1 //
   2 // System.Xml.XmlWriter
   3 //
   4 // Authors:
   5 //   Kral Ferch <kral_ferch@hotmail.com>
   6 //   Atsushi Enomoto <ginga@kit.hi-ho.ne.jp>
   7 //
   8 // (C) 2002 Kral Ferch
   9 // (C) 2002-2003 Atsushi Enomoto
  10 // (C) 2004-2007 Novell, Inc.
  11 //
  12
  13 //
  14 // Permission is hereby granted, free of charge, to any person obtaining
  15 // a copy of this software and associated documentation files (the
  16 // "Software"), to deal in the Software without restriction, including
  17 // without limitation the rights to use, copy, modify, merge, publish,
  18 // distribute, sublicense, and/or sell copies of the Software, and to
  19 // permit persons to whom the Software is furnished to do so, subject to
  20 // the following conditions:
  21 //
  22 // The above copyright notice and this permission notice shall be
  23 // included in all copies or substantial portions of the Software.
  24 //
  25 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  26 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  27 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  28 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  29 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  30 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  31 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  32 //
  33
  34 using System;
  35 using System.Collections;
  36 using System.IO;
  37 using System.Text;
  38 #if !MOONLIGHT
  39 using System.Xml.XPath;
  40 #endif
  41
  42 namespace System.Xml
  43 {
  44         public abstract class XmlWriter : IDisposable
  45         {
  46 #if NET_2_0
  47                 XmlWriterSettings settings;
  48 #endif
  49
  50                 #region Constructors
  51
  52                 protected XmlWriter () { }
  53
  54                 #endregion
  55
  56                 #region Properties
  57
  58 #if NET_2_0
  59                 public virtual XmlWriterSettings Settings {
  60                         get { return settings; }
  61                 }
  62 #endif
  63
  64                 public abstract WriteState WriteState { get; }
  65
  66
  67 #if NET_2_0
  68                 public virtual string XmlLang {
  69                         get { return null; }
  70                 }
  71
  72                 public virtual XmlSpace XmlSpace {
  73                         get { return XmlSpace.None; }
  74                 }
  75 #else
  76                 public abstract string XmlLang { get; }
  77
  78                 public abstract XmlSpace XmlSpace { get; }
  79 #endif
  80
  81                 #endregion
  82
  83                 #region Methods
  84
  85                 public abstract void Close ();
  86
  87 #if NET_2_0
  88                 public static XmlWriter Create (Stream stream)
  89                 {
  90                         return Create (stream, null);
  91                 }
  92
  93                 public static XmlWriter Create (string file)
  94                 {
  95                         return Create (file, null);
  96                 }
  97
  98                 public static XmlWriter Create (TextWriter writer)
  99                 {
 100                         return Create (writer, null);
 101                 }
 102
 103                 public static XmlWriter Create (XmlWriter writer)
 104                 {
 105                         return Create (writer, null);
 106                 }
 107
 108                 public static XmlWriter Create (StringBuilder builder)
 109                 {
 110                         return Create (builder, null);
 111                 }
 112
 113                 public static XmlWriter Create (Stream stream, XmlWriterSettings settings)
 114                 {
 115                         Encoding enc = settings != null ? settings.Encoding : Encoding.UTF8;
 116                         return Create (new StreamWriter (stream, enc), settings);
 117                 }
 118
 119                 public static XmlWriter Create (string file, XmlWriterSettings settings)
 120                 {
 121                         Encoding enc = settings != null ? settings.Encoding : Encoding.UTF8;
 122                         return CreateTextWriter (new StreamWriter (file, false, enc), settings, true);
 123                 }
 124
 125                 public static XmlWriter Create (StringBuilder builder, XmlWriterSettings settings)
 126                 {
 127                         return Create (new StringWriter (builder), settings);
 128                 }
 129
 130                 public static XmlWriter Create (TextWriter writer, XmlWriterSettings settings)
 131                 {
 132                         if (settings == null)
 133                                 settings = new XmlWriterSettings ();
 134                         return CreateTextWriter (writer, settings, settings.CloseOutput);
 135                 }
 136
 137                 public static XmlWriter Create (XmlWriter writer, XmlWriterSettings settings)
 138                 {
 139                         if (settings == null)
 140                                 settings = new XmlWriterSettings ();
 141                         else
 142                                 settings = settings.Clone ();
 143
 144                         var src = writer.Settings;
 145                         if (src == null) {
 146                                 settings.ConformanceLevel = ConformanceLevel.Document; // Huh? Why??
 147                                 writer = new DefaultXmlWriter (writer);
 148                                 writer.settings = settings;
 149                         } else {
 150                                 ConformanceLevel dst = src.ConformanceLevel;
 151                                 switch (src.ConformanceLevel) {
 152                                 case ConformanceLevel.Auto:
 153                                         dst = settings.ConformanceLevel;
 154                                         break;
 155                                 case ConformanceLevel.Document:
 156                                 case ConformanceLevel.Fragment:
 157                                         if (settings.ConformanceLevel != ConformanceLevel.Auto)
 158                                                 dst = settings.ConformanceLevel;
 159                                         break;
 160                                 }
 161
 162                                 settings.MergeFrom (src);
 163
 164                                 // It returns a new XmlWriter instance if 1) Settings is null, or 2) Settings ConformanceLevel (or might be other members as well) give significant difference.
 165                                 if (src.ConformanceLevel != dst) {
 166                                         writer = new DefaultXmlWriter (writer, false);
 167                                         writer.settings = settings;
 168                                 }
 169                         }
 170
 171                         return writer;
 172                 }
 173
 174                 private static XmlWriter CreateTextWriter (TextWriter writer, XmlWriterSettings settings, bool closeOutput)
 175                 {
 176                         if (settings == null)
 177                                 settings = new XmlWriterSettings ();
 178                         XmlTextWriter xtw = new XmlTextWriter (writer, settings, closeOutput);
 179                         return Create (xtw, settings);
 180                 }
 181
 182                 protected virtual void Dispose (bool disposing)
 183                 {
 184                         Close ();
 185                 }
 186
 187                 void IDisposable.Dispose ()
 188                 {
 189                         Dispose (false);
 190                 }
 191 #endif
 192
 193                 public abstract void Flush ();
 194
 195                 public abstract string LookupPrefix (string ns);
 196
 197                 private void WriteAttribute (XmlReader reader, bool defattr)
 198                 {
 199                         if (!defattr && reader.IsDefault)
 200                                 return;
 201
 202                         WriteStartAttribute (reader.Prefix, reader.LocalName, reader.NamespaceURI);
 203 #if MOONLIGHT
 204                         // no ReadAttributeValue() in 2.1 profile.
 205                         WriteString (reader.Value);
 206 #else
 207                         while (reader.ReadAttributeValue ()) {
 208                                 switch (reader.NodeType) {
 209                                 case XmlNodeType.Text:
 210                                         WriteString (reader.Value);
 211                                         break;
 212                                 case XmlNodeType.EntityReference:
 213                                         WriteEntityRef (reader.Name);
 214                                         break;
 215                                 }
 216                         }
 217 #endif
 218                         WriteEndAttribute ();
 219                 }
 220
 221                 public virtual void WriteAttributes (XmlReader reader, bool defattr)
 222                 {
 223                         if(reader == null)
 224                                 throw new ArgumentException("null XmlReader specified.", "reader");
 225
 226                         switch (reader.NodeType) {
 227                         case XmlNodeType.XmlDeclaration:
 228                                 WriteAttributeString ("version", reader ["version"]);
 229                                 if (reader ["encoding"] != null)
 230                                         WriteAttributeString ("encoding", reader ["encoding"]);
 231                                 if (reader ["standalone"] != null)
 232                                         WriteAttributeString ("standalone", reader ["standalone"]);
 233                                 break;
 234                         case XmlNodeType.Element:
 235                                 if (reader.MoveToFirstAttribute ())
 236                                         goto case XmlNodeType.Attribute;
 237                                 break;
 238                         case XmlNodeType.Attribute:
 239                                 do {
 240                                         WriteAttribute (reader, defattr);
 241                                 } while (reader.MoveToNextAttribute ());
 242                                 reader.MoveToElement ();
 243                                 break;
 244                         default:
 245                                 throw new XmlException("NodeType is not one of Element, Attribute, nor XmlDeclaration.");
 246                         }
 247                 }
 248
 249                 public void WriteAttributeString (string localName, string value)
 250                 {
 251                         WriteAttributeString ("", localName, null, value);
 252                 }
 253
 254                 public void WriteAttributeString (string localName, string ns, string value)
 255                 {
 256                         WriteAttributeString ("", localName, ns, value);
 257                 }
 258
 259                 public void WriteAttributeString (string prefix, string localName, string ns, string value)
 260                 {
 261                         // In MS.NET (1.0), this check is done *here*, not at WriteStartAttribute.
 262                         // (XmlTextWriter.WriteStartAttribute("xmlns", "anyname", null) throws an exception.
 263
 264                         WriteStartAttribute (prefix, localName, ns);
 265                         if (value != null && value.Length > 0)
 266                                 WriteString (value);
 267                         WriteEndAttribute ();
 268                 }
 269
 270                 public abstract void WriteBase64 (byte[] buffer, int index, int count);
 271
 272 #if NET_2_0
 273                 public virtual void WriteBinHex (byte [] buffer, int index, int count)
 274                 {
 275                         StringWriter sw = new StringWriter ();
 276                         XmlConvert.WriteBinHex (buffer, index, count, sw);
 277                         WriteString (sw.ToString ());
 278                 }
 279 #else
 280                 public abstract void WriteBinHex (byte[] buffer, int index, int count);
 281 #endif
 282
 283                 public abstract void WriteCData (string text);
 284
 285                 public abstract void WriteCharEntity (char ch);
 286
 287                 public abstract void WriteChars (char[] buffer, int index, int count);
 288
 289                 public abstract void WriteComment (string text);
 290
 291                 public abstract void WriteDocType (string name, string pubid, string sysid, string subset);
 292
 293                 public void WriteElementString (string localName, string value)
 294                 {
 295                         WriteStartElement(localName);
 296                         if (value != null && value.Length > 0)
 297                                 WriteString(value);
 298                         WriteEndElement();
 299                 }
 300
 301                 public void WriteElementString (string localName, string ns, string value)
 302                 {
 303                         WriteStartElement(localName, ns);
 304                         if (value != null && value.Length > 0)
 305                                 WriteString(value);
 306                         WriteEndElement();
 307                 }
 308
 309 #if NET_2_0
 310                 public void WriteElementString (string prefix, string localName, string ns, string value)
 311                 {
 312                         WriteStartElement(prefix, localName, ns);
 313                         if (value != null && value.Length > 0)
 314                                 WriteString(value);
 315                         WriteEndElement();
 316                 }
 317 #endif
 318
 319                 public abstract void WriteEndAttribute ();
 320
 321                 public abstract void WriteEndDocument ();
 322
 323                 public abstract void WriteEndElement ();
 324
 325                 public abstract void WriteEntityRef (string name);
 326
 327                 public abstract void WriteFullEndElement ();
 328
 329 #if NET_2_0
 330                 public virtual void WriteName (string name)
 331                 {
 332                         WriteNameInternal (name);
 333                 }
 334
 335                 public virtual void WriteNmToken (string name)
 336                 {
 337                         WriteNmTokenInternal (name);
 338                 }
 339
 340                 public virtual void WriteQualifiedName (string localName, string ns)
 341                 {
 342                         WriteQualifiedNameInternal (localName, ns);
 343                 }
 344 #else
 345                 public abstract void WriteName (string name);
 346
 347                 public abstract void WriteNmToken (string name);
 348
 349                 public abstract void WriteQualifiedName (string localName, string ns);
 350 #endif
 351
 352                 internal void WriteNameInternal (string name)
 353                 {
 354 #if NET_2_0
 355                         switch (Settings.ConformanceLevel) {
 356                         case ConformanceLevel.Document:
 357                         case ConformanceLevel.Fragment:
 358                                 XmlConvert.VerifyName (name);
 359                                 break;
 360                         }
 361 #else
 362                         XmlConvert.VerifyName (name);
 363 #endif
 364                         WriteString (name);
 365                 }
 366
 367                 internal virtual void WriteNmTokenInternal (string name)
 368                 {
 369                         bool valid = true;
 370 #if NET_2_0
 371                         switch (Settings.ConformanceLevel) {
 372                         case ConformanceLevel.Document:
 373                         case ConformanceLevel.Fragment:
 374                                 valid = XmlChar.IsNmToken (name);
 375                                         break;
 376                         }
 377 #else
 378                         valid = XmlChar.IsNmToken (name);
 379 #endif
 380                         if (!valid)
 381                                 throw new ArgumentException ("Argument name is not a valid NMTOKEN.");
 382                         WriteString (name);
 383                 }
 384
 385                 internal void WriteQualifiedNameInternal (string localName, string ns)
 386                 {
 387                         if (localName == null || localName == String.Empty)
 388                                 throw new ArgumentException ();
 389                         if (ns == null)
 390                                 ns = String.Empty;
 391
 392 #if NET_2_0
 393                         if (Settings != null) {
 394                                 switch (Settings.ConformanceLevel) {
 395                                 case ConformanceLevel.Document:
 396                                 case ConformanceLevel.Fragment:
 397                                         XmlConvert.VerifyNCName (localName);
 398                                         break;
 399                                 }
 400                         }
 401                         else
 402                                 XmlConvert.VerifyNCName (localName);
 403 #else
 404                         XmlConvert.VerifyNCName (localName);
 405 #endif
 406
 407                         string prefix = ns.Length > 0 ? LookupPrefix (ns) : String.Empty;
 408                         if (prefix == null)
 409                                 throw new ArgumentException (String.Format ("Namespace '{0}' is not declared.", ns));
 410
 411                         if (prefix != String.Empty) {
 412                                 WriteString (prefix);
 413                                 WriteString (":");
 414                                 WriteString (localName);
 415                         }
 416                         else
 417                                 WriteString (localName);
 418                 }
 419
 420 #if !MOONLIGHT
 421                 public virtual void WriteNode (XPathNavigator navigator, bool defattr)
 422                 {
 423                         if (navigator == null)
 424                                 throw new ArgumentNullException ("navigator");
 425                         switch (navigator.NodeType) {
 426                         case XPathNodeType.Attribute:
 427                                 // no operation
 428                                 break;
 429                         case XPathNodeType.Namespace:
 430                                 // no operation
 431                                 break;
 432                         case XPathNodeType.Text:
 433                                 WriteString (navigator.Value);
 434                                 break;
 435                         case XPathNodeType.SignificantWhitespace:
 436                                 WriteWhitespace (navigator.Value);
 437                                 break;
 438                         case XPathNodeType.Whitespace:
 439                                 WriteWhitespace (navigator.Value);
 440                                 break;
 441                         case XPathNodeType.Comment:
 442                                 WriteComment (navigator.Value);
 443                                 break;
 444                         case XPathNodeType.ProcessingInstruction:
 445                                 WriteProcessingInstruction (navigator.Name, navigator.Value);
 446                                 break;
 447                         case XPathNodeType.Root:
 448                                 if (navigator.MoveToFirstChild ()) {
 449                                         do {
 450                                                 WriteNode (navigator, defattr);
 451                                         } while (navigator.MoveToNext ());
 452                                         navigator.MoveToParent ();
 453                                 }
 454                                 break;
 455                         case XPathNodeType.Element:
 456                                 WriteStartElement (navigator.Prefix, navigator.LocalName, navigator.NamespaceURI);
 457                                 if (navigator.MoveToFirstNamespace (XPathNamespaceScope.Local)) {
 458                                         do {
 459                                                 if (defattr || navigator.SchemaInfo == null || navigator.SchemaInfo.IsDefault)
 460                                                         WriteAttributeString (navigator.Prefix,
 461                                                                 navigator.LocalName == String.Empty ? "xmlns" : navigator.LocalName,
 462                                                                 "http://www.w3.org/2000/xmlns/",
 463                                                                 navigator.Value);
 464                                         } while (navigator.MoveToNextNamespace (XPathNamespaceScope.Local));
 465                                         navigator.MoveToParent ();
 466                                 }
 467                                 if (navigator.MoveToFirstAttribute ()) {
 468                                         do {
 469                                                 if (defattr || navigator.SchemaInfo == null || navigator.SchemaInfo.IsDefault)
 470                                                         WriteAttributeString (navigator.Prefix, navigator.LocalName, navigator.NamespaceURI, navigator.Value);
 471
 472                                         } while (navigator.MoveToNextAttribute ());
 473                                         navigator.MoveToParent ();
 474                                 }
 475                                 if (navigator.MoveToFirstChild ()) {
 476                                         do {
 477                                                 WriteNode (navigator, defattr);
 478                                         } while (navigator.MoveToNext ());
 479                                         navigator.MoveToParent ();
 480                                 }
 481                                 if (navigator.IsEmptyElement)
 482                                         WriteEndElement ();
 483                                 else
 484                                         WriteFullEndElement ();
 485                                 break;
 486                         default:
 487                                 throw new NotSupportedException ();
 488                         }
 489                 }
 490 #endif
 491
 492                 public virtual void WriteNode (XmlReader reader, bool defattr)
 493                 {
 494                         if (reader == null)
 495                                 throw new ArgumentException ();
 496
 497                         if (reader.ReadState == ReadState.Initial) {
 498                                 reader.Read ();
 499                                 do {
 500                                         WriteNode (reader, defattr);
 501                                 } while (!reader.EOF);
 502                                 return;
 503                         }
 504
 505                         switch (reader.NodeType) {
 506                         case XmlNodeType.Element:
 507                                 WriteStartElement (reader.Prefix, reader.LocalName, reader.NamespaceURI);
 508 #if false
 509                                 WriteAttributes (reader, defattr);
 510                                 reader.MoveToElement ();
 511 #else
 512                                 // Well, I found that MS.NET took this way, since
 513                                 // there was a error-prone SgmlReader that fails
 514                                 // MoveToNextAttribute().
 515                                 if (reader.HasAttributes) {
 516                                         for (int i = 0; i < reader.AttributeCount; i++) {
 517                                                 reader.MoveToAttribute (i);
 518                                                 WriteAttribute (reader, defattr);
 519                                         }
 520                                         reader.MoveToElement ();
 521                                 }
 522 #endif
 523                                 if (reader.IsEmptyElement)
 524                                         WriteEndElement ();
 525                                 else {
 526                                         int depth = reader.Depth;
 527                                         reader.Read ();
 528                                         if (reader.NodeType != XmlNodeType.EndElement) {
 529                                                 do {
 530                                                         WriteNode (reader, defattr);
 531                                                 } while (depth < reader.Depth);
 532                                         }
 533                                         WriteFullEndElement ();
 534                                 }
 535                                 break;
 536                         // In case of XmlAttribute, don't proceed reader, and it will never be written.
 537                         case XmlNodeType.Attribute:
 538                                 return;
 539                         case XmlNodeType.Text:
 540                                 WriteString (reader.Value);
 541                                 break;
 542                         case XmlNodeType.CDATA:
 543                                 WriteCData (reader.Value);
 544                                 break;
 545                         case XmlNodeType.EntityReference:
 546                                 WriteEntityRef (reader.Name);
 547                                 break;
 548                         case XmlNodeType.XmlDeclaration:
 549                                 // LAMESPEC: It means that XmlWriter implementation _must not_ check
 550                                 // whether PI name is "xml" (it is XML error) or not.
 551                         case XmlNodeType.ProcessingInstruction:
 552                                 WriteProcessingInstruction (reader.Name, reader.Value);
 553                                 break;
 554                         case XmlNodeType.Comment:
 555                                 WriteComment (reader.Value);
 556                                 break;
 557                         case XmlNodeType.DocumentType:
 558                                 WriteDocType (reader.Name,
 559                                         reader ["PUBLIC"], reader ["SYSTEM"], reader.Value);
 560                                 break;
 561                         case XmlNodeType.SignificantWhitespace:
 562                                 goto case XmlNodeType.Whitespace;
 563                         case XmlNodeType.Whitespace:
 564                                 WriteWhitespace (reader.Value);
 565                                 break;
 566                         case XmlNodeType.EndElement:
 567                                 WriteFullEndElement ();
 568                                 break;
 569                         case XmlNodeType.EndEntity:
 570                                 break;
 571                         case XmlNodeType.None:
 572                                 break;  // Do nothing, nor reporting errors.
 573                         default:
 574                                 throw new XmlException ("Unexpected node " + reader.Name + " of type " + reader.NodeType);
 575                         }
 576                         reader.Read ();
 577                 }
 578
 579                 public abstract void WriteProcessingInstruction (string name, string text);
 580
 581                 public abstract void WriteRaw (string data);
 582
 583                 public abstract void WriteRaw (char[] buffer, int index, int count);
 584
 585 #if NET_2_0
 586                 public void WriteStartAttribute (string localName)
 587                 {
 588                         WriteStartAttribute (null, localName, null);
 589                 }
 590 #endif
 591
 592                 public void WriteStartAttribute (string localName, string ns)
 593                 {
 594                         WriteStartAttribute (null, localName, ns);
 595                 }
 596
 597                 public abstract void WriteStartAttribute (string prefix, string localName, string ns);
 598
 599                 public abstract void WriteStartDocument ();
 600
 601                 public abstract void WriteStartDocument (bool standalone);
 602
 603                 public void WriteStartElement (string localName)
 604                 {
 605                         WriteStartElement (null, localName, null);
 606                 }
 607
 608                 public void WriteStartElement (string localName, string ns)
 609                 {
 610                         WriteStartElement (null, localName, ns);
 611                 }
 612
 613                 public abstract void WriteStartElement (string prefix, string localName, string ns);
 614
 615                 public abstract void WriteString (string text);
 616
 617                 public abstract void WriteSurrogateCharEntity (char lowChar, char highChar);
 618
 619                 public abstract void WriteWhitespace (string ws);
 620
 621 #if NET_2_0
 622                 public virtual void WriteValue (bool value)
 623                 {
 624                         WriteString (XQueryConvert.BooleanToString (value));
 625                 }
 626
 627                 public virtual void WriteValue (DateTime value)
 628                 {
 629                         WriteString (XmlConvert.ToString (value));
 630                 }
 631
 632                 public virtual void WriteValue (decimal value)
 633                 {
 634                         WriteString (XQueryConvert.DecimalToString (value));
 635                 }
 636
 637                 public virtual void WriteValue (double value)
 638                 {
 639                         WriteString (XQueryConvert.DoubleToString (value));
 640                 }
 641
 642                 public virtual void WriteValue (int value)
 643                 {
 644                         WriteString (XQueryConvert.IntToString (value));
 645                 }
 646
 647                 public virtual void WriteValue (long value)
 648                 {
 649                         WriteString (XQueryConvert.IntegerToString (value));
 650                 }
 651
 652                 public virtual void WriteValue (object value)
 653                 {
 654                         if (value == null)
 655                                 throw new ArgumentNullException ("value");
 656
 657                         if (value is string)
 658                                 WriteString ((string) value);
 659                         else if (value is bool)
 660                                 WriteValue ((bool) value);
 661                         else if (value is byte)
 662                                 WriteValue ((int) value);
 663                         else if (value is byte [])
 664                                 WriteBase64 ((byte []) value, 0, ((byte []) value).Length);
 665                         else if (value is char [])
 666                                 WriteChars ((char []) value, 0, ((char []) value).Length);
 667                         else if (value is DateTime)
 668                                 WriteValue ((DateTime) value);
 669                         else if (value is decimal)
 670                                 WriteValue ((decimal) value);
 671                         else if (value is double)
 672                                 WriteValue ((double) value);
 673                         else if (value is short)
 674                                 WriteValue ((int) value);
 675                         else if (value is int)
 676                                 WriteValue ((int) value);
 677                         else if (value is long)
 678                                 WriteValue ((long) value);
 679                         else if (value is float)
 680                                 WriteValue ((float) value);
 681                         else if (value is TimeSpan) // undocumented
 682                                 WriteString (XmlConvert.ToString ((TimeSpan) value));
 683                         else if (value is Uri)
 684                                 WriteString (((Uri) value).ToString ());
 685                         else if (value is XmlQualifiedName) {
 686                                 XmlQualifiedName qname = (XmlQualifiedName) value;
 687                                 if (!qname.Equals (XmlQualifiedName.Empty)) {
 688                                         if (qname.Namespace.Length > 0 && LookupPrefix (qname.Namespace) == null)
 689                                                 throw new InvalidCastException (String.Format ("The QName '{0}' cannot be written. No corresponding prefix is declared", qname));
 690                                         WriteQualifiedName (qname.Name, qname.Namespace);
 691                                 }
 692                                 else
 693                                         WriteString (String.Empty);
 694                         }
 695                         else if (value is IEnumerable) {
 696                                 bool follow = false;
 697                                 foreach (object obj in (IEnumerable) value) {
 698                                         if (follow)
 699                                                 WriteString (" ");
 700                                         else
 701                                                 follow = true;
 702                                         WriteValue (obj);
 703                                 }
 704                         }
 705                         else
 706                                 throw new InvalidCastException (String.Format ("Type '{0}' cannot be cast to string", value.GetType ()));
 707                 }
 708
 709                 public virtual void WriteValue (float value)
 710                 {
 711                         WriteString (XQueryConvert.FloatToString (value));
 712                 }
 713
 714                 public virtual void WriteValue (string value)
 715                 {
 716                         WriteString (value);
 717                 }
 718 #endif
 719
 720                 #endregion
 721         }
 722 }