mcs/class/System.Xaml/System.Xaml/XamlType.cs

   1 //
   2 // Copyright (C) 2010 Novell Inc. http://novell.com
   3 //
   4 // Permission is hereby granted, free of charge, to any person obtaining
   5 // a copy of this software and associated documentation files (the
   6 // "Software"), to deal in the Software without restriction, including
   7 // without limitation the rights to use, copy, modify, merge, publish,
   8 // distribute, sublicense, and/or sell copies of the Software, and to
   9 // permit persons to whom the Software is furnished to do so, subject to
  10 // the following conditions:
  11 //
  12 // The above copyright notice and this permission notice shall be
  13 // included in all copies or substantial portions of the Software.
  14 //
  15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  19 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  20 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  21 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  22 //
  23 using System;
  24 using System.Collections;
  25 using System.Collections.Generic;
  26 using System.ComponentModel;
  27 using System.Linq;
  28 using System.Reflection;
  29 using System.Windows.Markup;
  30 using System.Xaml.Schema;
  31
  32 namespace System.Xaml
  33 {
  34         public class XamlType : IEquatable<XamlType>
  35         {
  36                 public XamlType (Type underlyingType, XamlSchemaContext schemaContext)
  37                         : this (underlyingType, schemaContext, null)
  38                 {
  39                 }
  40
  41 //              static readonly Type [] predefined_types = {
  42 //                              typeof (XData), typeof (Uri), typeof (TimeSpan), typeof (PropertyDefinition), typeof (MemberDefinition), typeof (Reference)
  43 //                      };
  44
  45                 public XamlType (Type underlyingType, XamlSchemaContext schemaContext, XamlTypeInvoker invoker)
  46                         : this (schemaContext, invoker)
  47                 {
  48                         if (underlyingType == null)
  49                                 throw new ArgumentNullException ("underlyingType");
  50                         type = underlyingType;
  51                         underlying_type = type;
  52
  53                         XamlType xt;
  54                         if (XamlLanguage.InitializingTypes) {
  55                                 Name = type.GetXamlName ();
  56                                 PreferredXamlNamespace = XamlLanguage.Xaml2006Namespace;
  57                         } else if ((xt = XamlLanguage.AllTypes.FirstOrDefault (t => t.UnderlyingType == type)) != null) {
  58                                 Name = xt.Name;
  59                                 PreferredXamlNamespace = XamlLanguage.Xaml2006Namespace;
  60                         } else {
  61                                 Name = type.GetXamlName ();
  62                                 PreferredXamlNamespace = String.Format ("clr-namespace:{0};assembly={1}", type.Namespace, type.Assembly.GetName ().Name);
  63                         }
  64                 }
  65
  66                 public XamlType (string unknownTypeNamespace, string unknownTypeName, IList<XamlType> typeArguments, XamlSchemaContext schemaContext)
  67                         : this (schemaContext, null)
  68                 {
  69                         if (unknownTypeNamespace == null)
  70                                 throw new ArgumentNullException ("unknownTypeNamespace");
  71                         if (unknownTypeName == null)
  72                                 throw new ArgumentNullException ("unknownTypeName");
  73                         if (schemaContext == null)
  74                                 throw new ArgumentNullException ("schemaContext");
  75
  76                         type = typeof (object);
  77                         Name = unknownTypeName;
  78                         PreferredXamlNamespace = unknownTypeNamespace;
  79                         TypeArguments = typeArguments != null && typeArguments.Count == 0 ? null : typeArguments;
  80                         explicit_ns = unknownTypeNamespace;
  81                 }
  82
  83                 protected XamlType (string typeName, IList<XamlType> typeArguments, XamlSchemaContext schemaContext)
  84                         : this (String.Empty, typeName, typeArguments, schemaContext)
  85                 {
  86                 }
  87
  88                 XamlType (XamlSchemaContext schemaContext, XamlTypeInvoker invoker)
  89                 {
  90                         if (schemaContext == null)
  91                                 throw new ArgumentNullException ("schemaContext");
  92                         SchemaContext = schemaContext;
  93                         this.invoker = invoker ?? new XamlTypeInvoker (this);
  94                 }
  95
  96                 Type type, underlying_type;
  97
  98                 string explicit_ns;
  99
 100                 // populated properties
 101                 XamlType base_type;
 102                 XamlTypeInvoker invoker;
 103
 104                 internal EventHandler<XamlSetMarkupExtensionEventArgs> SetMarkupExtensionHandler {
 105                         get { return LookupSetMarkupExtensionHandler (); }
 106                 }
 107
 108                 internal EventHandler<XamlSetTypeConverterEventArgs> SetTypeConverterHandler {
 109                         get { return LookupSetTypeConverterHandler (); }
 110                 }
 111
 112                 public IList<XamlType> AllowedContentTypes {
 113                         get { return LookupAllowedContentTypes (); }
 114                 }
 115
 116                 public XamlType BaseType {
 117                         get { return LookupBaseType (); }
 118                 }
 119
 120                 public bool ConstructionRequiresArguments {
 121                         get { return LookupConstructionRequiresArguments (); }
 122                 }
 123
 124                 public XamlMember ContentProperty {
 125                         get { return LookupContentProperty (); }
 126                 }
 127
 128                 public IList<XamlType> ContentWrappers {
 129                         get { return LookupContentWrappers (); }
 130                 }
 131
 132                 public XamlValueConverter<XamlDeferringLoader> DeferringLoader {
 133                         get { return LookupDeferringLoader (); }
 134                 }
 135
 136                 public XamlTypeInvoker Invoker {
 137                         get { return LookupInvoker (); }
 138                 }
 139
 140                 public bool IsAmbient {
 141                         get { return LookupIsAmbient (); }
 142                 }
 143
 144                 public bool IsArray {
 145                         get { return LookupCollectionKind () == XamlCollectionKind.Array; }
 146                 }
 147
 148                 // it somehow treats array as not a collection...
 149                 public bool IsCollection {
 150                         get { return LookupCollectionKind () == XamlCollectionKind.Collection; }
 151                 }
 152
 153                 public bool IsConstructible {
 154                         get { return LookupIsConstructible (); }
 155                 }
 156
 157                 public bool IsDictionary {
 158                         get { return LookupCollectionKind () == XamlCollectionKind.Dictionary; }
 159                 }
 160
 161                 public bool IsGeneric {
 162                         get { return type.IsGenericType; }
 163                 }
 164
 165                 public bool IsMarkupExtension {
 166                         get { return LookupIsMarkupExtension (); }
 167                 }
 168                 public bool IsNameScope {
 169                         get { return LookupIsNameScope (); }
 170                 }
 171                 public bool IsNameValid {
 172                         get { return XamlLanguage.IsValidXamlName (Name); }
 173                 }
 174
 175                 public bool IsNullable {
 176                         get { return LookupIsNullable (); }
 177                 }
 178
 179                 public bool IsPublic {
 180                         get { return LookupIsPublic (); }
 181                 }
 182
 183                 public bool IsUnknown {
 184                         get { return LookupIsUnknown (); }
 185                 }
 186
 187                 public bool IsUsableDuringInitialization {
 188                         get { return LookupUsableDuringInitialization (); }
 189                 }
 190
 191                 public bool IsWhitespaceSignificantCollection {
 192                         get { return LookupIsWhitespaceSignificantCollection (); }
 193                 }
 194
 195                 public bool IsXData {
 196                         get { return LookupIsXData (); }
 197                 }
 198
 199                 public XamlType ItemType {
 200                         get { return LookupItemType (); }
 201                 }
 202
 203                 public XamlType KeyType {
 204                         get { return LookupKeyType (); }
 205                 }
 206
 207                 public XamlType MarkupExtensionReturnType {
 208                         get { return LookupMarkupExtensionReturnType (); }
 209                 }
 210
 211                 public string Name { get; private set; }
 212
 213                 public string PreferredXamlNamespace { get; private set; }
 214
 215                 public XamlSchemaContext SchemaContext { get; private set; }
 216
 217                 public bool TrimSurroundingWhitespace {
 218                         get { return LookupTrimSurroundingWhitespace (); }
 219                 }
 220
 221                 public IList<XamlType> TypeArguments { get; private set; }
 222
 223                 public XamlValueConverter<TypeConverter> TypeConverter {
 224                         get { return LookupTypeConverter (); }
 225                 }
 226
 227                 public Type UnderlyingType {
 228                         get { return LookupUnderlyingType (); }
 229                 }
 230
 231                 public XamlValueConverter<ValueSerializer> ValueSerializer {
 232                         get { return LookupValueSerializer (); }
 233                 }
 234
 235                 internal string InternalXmlName {
 236                         get {
 237                                 var stn = XamlLanguage.SpecialNames.FirstOrDefault (s => s.Type == this);
 238                                 return stn != null ? stn.Name : Name;
 239                         }
 240                 }
 241
 242                 public static bool operator == (XamlType left, XamlType right)
 243                 {
 244                         return IsNull (left) ? IsNull (right) : left.Equals (right);
 245                 }
 246
 247                 static bool IsNull (XamlType a)
 248                 {
 249                         return Object.ReferenceEquals (a, null);
 250                 }
 251
 252                 public static bool operator != (XamlType left, XamlType right)
 253                 {
 254                         return !(left == right);
 255                 }
 256
 257                 public bool Equals (XamlType other)
 258                 {
 259                         return !IsNull (other) &&
 260                                 UnderlyingType == other.UnderlyingType &&
 261                                 Name == other.Name &&
 262                                 PreferredXamlNamespace == other.PreferredXamlNamespace && TypeArguments.ListEquals (other.TypeArguments);
 263                 }
 264
 265                 public override bool Equals (object obj)
 266                 {
 267                         var a = obj as XamlType;
 268                         return Equals (a);
 269                 }
 270
 271                 public override int GetHashCode ()
 272                 {
 273                         if (UnderlyingType != null)
 274                                 return UnderlyingType.GetHashCode ();
 275                         int x = Name.GetHashCode () << 7 + PreferredXamlNamespace.GetHashCode ();
 276                         if (TypeArguments != null)
 277                                 foreach (var t in TypeArguments)
 278                                         x = t.GetHashCode () + x << 5;
 279                         return x;
 280                 }
 281
 282                 public override string ToString ()
 283                 {
 284                         return String.IsNullOrEmpty (PreferredXamlNamespace) ? Name : String.Concat ("{", PreferredXamlNamespace, "}", Name);
 285                 }
 286
 287                 public virtual bool CanAssignTo (XamlType xamlType)
 288                 {
 289                         throw new NotImplementedException ();
 290                 }
 291
 292                 public XamlMember GetAliasedProperty (XamlDirective directive)
 293                 {
 294                         return LookupAliasedProperty (directive);
 295                 }
 296
 297                 public ICollection<XamlMember> GetAllAttachableMembers ()
 298                 {
 299                         return new List<XamlMember> (LookupAllAttachableMembers ());
 300                 }
 301
 302                 public ICollection<XamlMember> GetAllMembers ()
 303                 {
 304                         return new List<XamlMember> (LookupAllMembers ());
 305                 }
 306
 307                 public XamlMember GetAttachableMember (string name)
 308                 {
 309                         return LookupAttachableMember (name);
 310                 }
 311
 312                 public XamlMember GetMember (string name)
 313                 {
 314                         return LookupMember (name, false);
 315                 }
 316
 317                 public IList<XamlType> GetPositionalParameters (int parameterCount)
 318                 {
 319                         return LookupPositionalParameters (parameterCount);
 320                 }
 321
 322                 public virtual IList<string> GetXamlNamespaces ()
 323                 {
 324                         throw new NotImplementedException ();
 325                         /* this does not work like documented!
 326                         if (explicit_ns != null)
 327                                 return new string [] {explicit_ns};
 328                         var l = SchemaContext.GetAllXamlNamespaces ();
 329                         if (l != null)
 330                                 return new List<string> (l);
 331                         return new string [] {String.Empty};
 332                         */
 333                 }
 334
 335                 // lookups
 336
 337                 protected virtual XamlMember LookupAliasedProperty (XamlDirective directive)
 338                 {
 339                         if (directive == XamlLanguage.Key) {
 340                                 var a = this.GetCustomAttribute<DictionaryKeyPropertyAttribute> ();
 341                                 return a != null ? GetMember (a.Name) : null;
 342                         }
 343                         if (directive == XamlLanguage.Name) {
 344                                 var a = this.GetCustomAttribute<RuntimeNamePropertyAttribute> ();
 345                                 return a != null ? GetMember (a.Name) : null;
 346                         }
 347                         if (directive == XamlLanguage.Uid) {
 348                                 var a = this.GetCustomAttribute<UidPropertyAttribute> ();
 349                                 return a != null ? GetMember (a.Name) : null;
 350                         }
 351                         if (directive == XamlLanguage.Lang) {
 352                                 var a = this.GetCustomAttribute<XmlLangPropertyAttribute> ();
 353                                 return a != null ? GetMember (a.Name) : null;
 354                         }
 355                         return null;
 356                 }
 357
 358                 protected virtual IEnumerable<XamlMember> LookupAllAttachableMembers ()
 359                 {
 360                         if (UnderlyingType == null)
 361                                 return BaseType != null ? BaseType.GetAllAttachableMembers () : null;
 362                         return DoLookupAllAttachableMembers ();
 363                 }
 364
 365                 IEnumerable<XamlMember> DoLookupAllAttachableMembers ()
 366                 {
 367                         yield break; // FIXME: what to return here?
 368                 }
 369
 370                 static readonly XamlMember [] empty_array = new XamlMember [0];
 371
 372                 protected virtual IEnumerable<XamlMember> LookupAllMembers ()
 373                 {
 374                         if (UnderlyingType == null)
 375                                 return BaseType != null ? BaseType.GetAllMembers () : empty_array;
 376                         if (all_members_cache == null)
 377                                 all_members_cache = new List<XamlMember> (DoLookupAllMembers ());
 378                         return all_members_cache;
 379                 }
 380
 381                 List<XamlMember> all_members_cache;
 382
 383                 IEnumerable<XamlMember> DoLookupAllMembers ()
 384                 {
 385                         // This is a hack that is likely required due to internal implementation difference in System.Uri. Our Uri has two readonly collection properties
 386                         if (this == XamlLanguage.Uri)
 387                                 yield break;
 388
 389                         var bf = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
 390
 391                         foreach (var pi in UnderlyingType.GetProperties (bf))
 392                                 if (pi.CanRead && (pi.CanWrite && pi.GetIndexParameters ().Length == 0 || IsCollectionType (pi.PropertyType)))
 393                                         yield return new XamlMember (pi, SchemaContext);
 394                         foreach (var ei in UnderlyingType.GetEvents (bf))
 395                                 yield return new XamlMember (ei, SchemaContext);
 396                 }
 397
 398                 static bool IsCollectionType (Type type)
 399                 {
 400                         if (type == null)
 401                                 return false;
 402                         if (type.IsArray)
 403                                 return true;
 404
 405                         Type [] ifaces = type.GetInterfaces ();
 406                         foreach (Type i in ifaces)
 407                                 if (i.IsGenericType && i.GetGenericTypeDefinition ().Equals (typeof (ICollection<>)))
 408                                         return true;
 409                         foreach (Type i in ifaces)
 410                                 if (i == typeof (IList))
 411                                         return true;
 412
 413                         foreach (var iface in type.GetInterfaces ())
 414                                 if (iface == typeof (IDictionary) || (iface.IsGenericType && iface.GetGenericTypeDefinition () == typeof (IDictionary<,>)))
 415                                         return true;
 416
 417                         return false;
 418                 }
 419
 420                 protected virtual IList<XamlType> LookupAllowedContentTypes ()
 421                 {
 422                         // the actual implementation is very different from what is documented :(
 423                         return null;
 424
 425                         /*
 426                         var l = new List<XamlType> ();
 427                         if (ContentWrappers != null)
 428                                 l.AddRange (ContentWrappers);
 429                         if (ContentProperty != null)
 430                                 l.Add (ContentProperty.Type);
 431                         if (ItemType != null)
 432                                 l.Add (ItemType);
 433                         return l.Count > 0 ? l : null;
 434                         */
 435                 }
 436
 437                 protected virtual XamlMember LookupAttachableMember (string name)
 438                 {
 439                         throw new NotImplementedException ();
 440                 }
 441
 442                 [MonoTODO]
 443                 protected virtual XamlType LookupBaseType ()
 444                 {
 445                         if (base_type == null) {
 446                                 if (UnderlyingType == null)
 447                                         // FIXME: probably something advanced is needed here.
 448                                         base_type = new XamlType (typeof (object), SchemaContext, Invoker);
 449                                 else
 450                                         base_type = type.BaseType == null || type.BaseType == typeof (object) ? null : new XamlType (type.BaseType, SchemaContext, Invoker);
 451                         }
 452                         return base_type;
 453                 }
 454
 455                 // This implementation is not verified. (No place to use.)
 456                 protected virtual XamlCollectionKind LookupCollectionKind ()
 457                 {
 458                         if (UnderlyingType == null)
 459                                 return BaseType != null ? BaseType.LookupCollectionKind () : XamlCollectionKind.None;
 460                         if (type.IsArray)
 461                                 return XamlCollectionKind.Array;
 462
 463                         if (type.ImplementsAnyInterfacesOf (typeof (IDictionary), typeof (IDictionary<,>)))
 464                                 return XamlCollectionKind.Dictionary;
 465
 466                         if (type.ImplementsAnyInterfacesOf (typeof (ICollection), typeof (ICollection<>)))
 467                                 return XamlCollectionKind.Collection;
 468
 469                         return XamlCollectionKind.None;
 470                 }
 471
 472                 protected virtual bool LookupConstructionRequiresArguments ()
 473                 {
 474                         if (UnderlyingType == null)
 475                                 return false;
 476
 477                         // not sure if it is required, but MemberDefinition return true while they are abstract and it makes no sense.
 478                         if (UnderlyingType.IsAbstract)
 479                                 return true;
 480
 481                         // FIXME: probably some primitive types are treated as special.
 482                         switch (Type.GetTypeCode (UnderlyingType)) {
 483                         case TypeCode.String:
 484                                 return true;
 485                         case TypeCode.Object:
 486                                 if (UnderlyingType == typeof (TimeSpan))
 487                                         return false;
 488                                 break;
 489                         default:
 490                                 return false;
 491                         }
 492
 493                         return UnderlyingType.GetConstructor (BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance, null, Type.EmptyTypes, null) == null;
 494                 }
 495
 496                 protected virtual XamlMember LookupContentProperty ()
 497                 {
 498                         var a = this.GetCustomAttribute<ContentPropertyAttribute> ();
 499                         return a != null && a.Name != null ? GetMember (a.Name) : null;
 500                 }
 501
 502                 protected virtual IList<XamlType> LookupContentWrappers ()
 503                 {
 504                         if (CustomAttributeProvider == null)
 505                                 return null;
 506
 507                         var arr = CustomAttributeProvider.GetCustomAttributes (typeof (ContentWrapperAttribute), false);
 508                         if (arr == null || arr.Length == 0)
 509                                 return null;
 510                         var l = new XamlType [arr.Length];
 511                         for (int i = 0; i < l.Length; i++)
 512                                 l [i] = SchemaContext.GetXamlType (((ContentWrapperAttribute) arr [i]).ContentWrapper);
 513                         return l;
 514                 }
 515
 516                 internal ICustomAttributeProvider CustomAttributeProvider {
 517                         get { return LookupCustomAttributeProvider (); }
 518                 }
 519
 520                 protected virtual ICustomAttributeProvider LookupCustomAttributeProvider ()
 521                 {
 522                         return UnderlyingType;
 523                 }
 524                 protected virtual XamlValueConverter<XamlDeferringLoader> LookupDeferringLoader ()
 525                 {
 526                         throw new NotImplementedException ();
 527                 }
 528
 529                 protected virtual XamlTypeInvoker LookupInvoker ()
 530                 {
 531                         return invoker;
 532                 }
 533
 534                 protected virtual bool LookupIsAmbient ()
 535                 {
 536                         return this.GetCustomAttribute<AmbientAttribute> () != null;
 537                 }
 538
 539                 // It is documented as if it were to reflect spec. section 5.2,
 540                 // but the actual behavior shows it is *totally* wrong.
 541                 // Here I have implemented this based on the nunit test results. sigh.
 542                 protected virtual bool LookupIsConstructible ()
 543                 {
 544                         if (UnderlyingType == null)
 545                                 return true;
 546                         if (IsMarkupExtension)
 547                                 return true;
 548                         if (UnderlyingType.IsAbstract)
 549                                 return false;
 550                         if (!IsNameValid)
 551                                 return false;
 552                         return true;
 553                 }
 554
 555                 protected virtual bool LookupIsMarkupExtension ()
 556                 {
 557                         return typeof (MarkupExtension).IsAssignableFrom (UnderlyingType);
 558                 }
 559
 560                 protected virtual bool LookupIsNameScope ()
 561                 {
 562                         return typeof (INameScope).IsAssignableFrom (UnderlyingType);
 563                 }
 564
 565                 protected virtual bool LookupIsNullable ()
 566                 {
 567                         return !type.IsValueType || type.ImplementsInterface (typeof (Nullable<>));
 568                 }
 569
 570                 protected virtual bool LookupIsPublic ()
 571                 {
 572                         return underlying_type == null || underlying_type.IsPublic || underlying_type.IsNestedPublic;
 573                 }
 574
 575                 protected virtual bool LookupIsUnknown ()
 576                 {
 577                         return UnderlyingType == null;
 578                 }
 579
 580                 protected virtual bool LookupIsWhitespaceSignificantCollection ()
 581                 {
 582                         // probably for unknown types, it should preserve whitespaces.
 583                         return IsUnknown || this.GetCustomAttribute<WhitespaceSignificantCollectionAttribute> () != null;
 584                 }
 585
 586                 protected virtual bool LookupIsXData ()
 587                 {
 588                         // huh? XamlLanguage.XData.IsXData returns false(!)
 589                         // return typeof (XData).IsAssignableFrom (UnderlyingType);
 590                         return false;
 591                 }
 592
 593                 protected virtual XamlType LookupItemType ()
 594                 {
 595                         if (IsArray)
 596                                 return new XamlType (type.GetElementType (), SchemaContext);
 597                         if (IsDictionary) {
 598                                 if (!IsGeneric)
 599                                         return new XamlType (typeof (object), SchemaContext);
 600                                 return new XamlType (type.GetGenericArguments () [1], SchemaContext);
 601                         }
 602                         if (!IsCollection)
 603                                 return null;
 604                         if (!IsGeneric)
 605                                 return new XamlType (typeof (object), SchemaContext);
 606                         return new XamlType (type.GetGenericArguments () [0], SchemaContext);
 607                 }
 608
 609                 protected virtual XamlType LookupKeyType ()
 610                 {
 611                         if (!IsDictionary)
 612                                 return null;
 613                         if (!IsGeneric)
 614                                 return new XamlType (typeof (object), SchemaContext);
 615                         return new XamlType (type.GetGenericArguments () [0], SchemaContext);
 616                 }
 617
 618                 protected virtual XamlType LookupMarkupExtensionReturnType ()
 619                 {
 620                         var a = this.GetCustomAttribute<MarkupExtensionReturnTypeAttribute> ();
 621                         return a != null ? new XamlType (a.ReturnType, SchemaContext) : null;
 622                 }
 623
 624                 protected virtual XamlMember LookupMember (string name, bool skipReadOnlyCheck)
 625                 {
 626                         // FIXME: verify if this does not filter out events.
 627                         return GetAllMembers ().FirstOrDefault (m => m.Name == name && (skipReadOnlyCheck || !m.IsReadOnly || m.Type.IsCollection || m.Type.IsDictionary || m.Type.IsArray));
 628                 }
 629
 630                 protected virtual IList<XamlType> LookupPositionalParameters (int parameterCount)
 631                 {
 632                         if (UnderlyingType == null/* || !IsMarkupExtension*/) // see nunit tests...
 633                                 return null;
 634
 635                         // check if there is applicable ConstructorArgumentAttribute.
 636                         // If there is, then return its type.
 637                         if (parameterCount == 1) {
 638                                 foreach (var xm in GetAllMembers ()) {
 639                                         var ca = xm.CustomAttributeProvider.GetCustomAttribute<ConstructorArgumentAttribute> (false);
 640                                         if (ca != null)
 641                                                 return new XamlType [] {xm.Type};
 642                                 }
 643                         }
 644
 645                         var methods = (from m in UnderlyingType.GetConstructors (BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance) where m.GetParameters ().Length == parameterCount select m).ToArray ();
 646                         if (methods.Length == 1)
 647                                 return (from p in methods [0].GetParameters () select SchemaContext.GetXamlType (p.ParameterType)).ToArray ();
 648
 649                         if (SchemaContext.SupportMarkupExtensionsWithDuplicateArity)
 650                                 throw new NotSupportedException ("The default LookupPositionalParameters implementation does not allow duplicate arity of markup extensions");
 651                         return null;
 652                 }
 653
 654                 BindingFlags flags_get_static = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static;
 655
 656                 protected virtual EventHandler<XamlSetMarkupExtensionEventArgs> LookupSetMarkupExtensionHandler ()
 657                 {
 658                         var a = this.GetCustomAttribute<XamlSetMarkupExtensionAttribute> ();
 659                         if (a == null)
 660                                 return null;
 661                         var mi = type.GetMethod (a.XamlSetMarkupExtensionHandler, flags_get_static);
 662                         if (mi == null)
 663                                 throw new ArgumentException ("Binding to XamlSetMarkupExtensionHandler failed");
 664                         return (EventHandler<XamlSetMarkupExtensionEventArgs>) Delegate.CreateDelegate (typeof (EventHandler<XamlSetMarkupExtensionEventArgs>), mi);
 665                 }
 666
 667                 protected virtual EventHandler<XamlSetTypeConverterEventArgs> LookupSetTypeConverterHandler ()
 668                 {
 669                         var a = this.GetCustomAttribute<XamlSetTypeConverterAttribute> ();
 670                         if (a == null)
 671                                 return null;
 672                         var mi = type.GetMethod (a.XamlSetTypeConverterHandler, flags_get_static);
 673                         if (mi == null)
 674                                 throw new ArgumentException ("Binding to XamlSetTypeConverterHandler failed");
 675                         return (EventHandler<XamlSetTypeConverterEventArgs>) Delegate.CreateDelegate (typeof (EventHandler<XamlSetTypeConverterEventArgs>), mi);
 676                 }
 677
 678                 protected virtual bool LookupTrimSurroundingWhitespace ()
 679                 {
 680                         return this.GetCustomAttribute<TrimSurroundingWhitespaceAttribute> () != null;
 681                 }
 682
 683                 protected virtual XamlValueConverter<TypeConverter> LookupTypeConverter ()
 684                 {
 685                         var t = UnderlyingType;
 686                         if (t == null)
 687                                 return null;
 688
 689                         // equivalent to TypeExtension.
 690                         // FIXME: not sure if it should be specially handled here.
 691                         if (t == typeof (Type))
 692                                 t = typeof (TypeExtension);
 693
 694                         var a = CustomAttributeProvider.GetCustomAttribute<TypeConverterAttribute> (false);
 695                         if (a != null)
 696                                 return SchemaContext.GetValueConverter<TypeConverter> (Type.GetType (a.ConverterTypeName), this);
 697
 698                         if (t == typeof (object))
 699                                 return SchemaContext.GetValueConverter<TypeConverter> (typeof (TypeConverter), this);
 700
 701                         // It's still not decent to check CollectionConverter.
 702                         var tct = TypeDescriptor.GetConverter (t).GetType ();
 703                         if (tct != typeof (TypeConverter) && tct != typeof (CollectionConverter) && tct != typeof (ReferenceConverter))
 704                                 return SchemaContext.GetValueConverter<TypeConverter> (tct, this);
 705                         return null;
 706                 }
 707
 708                 protected virtual Type LookupUnderlyingType ()
 709                 {
 710                         return underlying_type;
 711                 }
 712
 713                 protected virtual bool LookupUsableDuringInitialization ()
 714                 {
 715                         var a = this.GetCustomAttribute<UsableDuringInitializationAttribute> ();
 716                         return a != null && a.Usable;
 717                 }
 718
 719                 static XamlValueConverter<ValueSerializer> string_value_serializer;
 720
 721                 protected virtual XamlValueConverter<ValueSerializer> LookupValueSerializer ()
 722                 {
 723                         return LookupValueSerializer (this, CustomAttributeProvider);
 724                 }
 725
 726                 internal static XamlValueConverter<ValueSerializer> LookupValueSerializer (XamlType targetType, ICustomAttributeProvider provider)
 727                 {
 728                         if (provider == null)
 729                                 return null;
 730
 731                         var a = provider.GetCustomAttribute<ValueSerializerAttribute> (true);
 732                         if (a != null)
 733                                 return new XamlValueConverter<ValueSerializer> (a.ValueSerializerType ?? Type.GetType (a.ValueSerializerTypeName), targetType);
 734
 735                         if (targetType.BaseType != null) {
 736                                 var ret = targetType.BaseType.LookupValueSerializer ();
 737                                 if (ret != null)
 738                                         return ret;
 739                         }
 740
 741                         if (targetType.UnderlyingType == typeof (string)) {
 742                                 if (string_value_serializer == null)
 743                                         string_value_serializer = new XamlValueConverter<ValueSerializer> (typeof (StringValueSerializer), targetType);
 744                                 return string_value_serializer;
 745                         }
 746
 747                         return null;
 748                 }
 749
 750                 internal IEnumerable<XamlMember> GetConstructorArguments ()
 751                 {
 752                         return GetAllMembers ().Where (m => m.UnderlyingMember != null && m.CustomAttributeProvider.GetCustomAttribute<ConstructorArgumentAttribute> (false) != null);
 753                 }
 754         }
 755 }