ReflectTypeDescriptionProvider.cs source code in C# .NET

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/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / CompMod / System / ComponentModel / ReflectTypeDescriptionProvider.cs / 3 / ReflectTypeDescriptionProvider.cs

                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.ComponentModel { 
 
    using System;
    using System.Collections; 
    using System.Collections.Generic;
    using System.ComponentModel.Design;
    using System.Diagnostics;
    using System.Globalization; 
    using System.Reflection;
    using System.Security; 
    using System.Security.Permissions; 

    ///  
    ///     This type description provider provides type information through
    ///     reflection.  Unless someone has provided a custom type description
    ///     provider for a type or instance, or unless an instance implements
    ///     ICustomTypeDescriptor, any query for type information will go through 
    ///     this class.  There should be a single instance of this class associated
    ///     with "object", as it can provide all type information for any type. 
    ///  
    [HostProtection(SharedState = true)]
    internal sealed class ReflectTypeDescriptionProvider : TypeDescriptionProvider 
    {
        // Hastable of Type -> ReflectedTypeData.  ReflectedTypeData contains all
        // of the type information we have gathered for a given type.
        // 
        private Hashtable _typeData;
 
        // This is the signature we look for when creating types that are generic, but 
        // want to know what type they are dealing with.  Enums are a good example of this;
        // there is one enum converter that can work with all enums, but it needs to know 
        // the type of enum it is dealing with.
        //
        private static Type[] _typeConstructor = new Type[] {typeof(Type)};
 
        // This is where we store the various converters, etc for the intrinsic types.
        // 
        private static Hashtable _editorTables; 
        private static Hashtable _intrinsicTypeConverters;
 
        // For converters, etc that are bound to class attribute data, rather than a class
        // type, we have special key sentinel values that we put into the hash table.
        //
        private static object _intrinsicReferenceKey = new object(); 
        private static object _intrinsicNullableKey = new object();
 
        // The key we put into IDictionaryService to store our cache dictionary. 
        //
        private static object _dictionaryKey = new object(); 

        // This is a cache on top of core reflection.  The cache
        // builds itself recursively, so if you ask for the properties
        // on Control, Component and object are also automatically filled 
        // in.  The keys to the property and event caches are types.
        // The keys to the attribute cache are either MemberInfos or types. 
        // 
        private static Hashtable _propertyCache;
        private static Hashtable _eventCache; 
        private static Hashtable _attributeCache;
        private static Hashtable _extendedPropertyCache;

        // These are keys we stuff into our object cache.  We use this 
        // cache data to store extender provider info for an object.
        // 
        private static readonly Guid _extenderProviderKey = Guid.NewGuid(); 
        private static readonly Guid _extenderPropertiesKey = Guid.NewGuid();
        private static readonly Guid _extenderProviderPropertiesKey = Guid.NewGuid(); 

        // These are attribute that, when we discover them on interfaces, we do
        // not merge them into the attribute set for a class.
        private static readonly Type[] _skipInterfaceAttributeList = new Type[] 
        {
            typeof(System.Runtime.InteropServices.GuidAttribute), 
            typeof(System.Runtime.InteropServices.ComVisibleAttribute), 
            typeof(System.Runtime.InteropServices.InterfaceTypeAttribute)
        }; 


        internal static Guid ExtenderProviderKey {
            get { 
                return _extenderProviderKey;
            } 
        } 

 
        private static object _internalSyncObject = new object();
        /// 
        ///     Creates a new ReflectTypeDescriptionProvider.  The type is the
        ///     type we will obtain type information for. 
        /// 
        internal ReflectTypeDescriptionProvider() 
        { 
            TypeDescriptor.Trace("Reflect : Creating ReflectTypeDescriptionProvider");
        } 

        /// 
        ///      This is a table we create for intrinsic types.
        ///      There should be entries here ONLY for intrinsic 
        ///      types, as all other types we should be able to
        ///      add attributes directly as metadata. 
        ///  
        private static Hashtable IntrinsicTypeConverters {
            get { 
                // It is not worth taking a lock for this -- worst case of a collision
                // would build two tables, one that garbage collects very quickly.
                //
                if (_intrinsicTypeConverters == null) { 
                    Hashtable temp = new Hashtable();
 
                    // Add the intrinsics 
                    //
                    temp[typeof(bool)] = typeof(BooleanConverter); 
                    temp[typeof(byte)] = typeof(ByteConverter);
                    temp[typeof(SByte)] = typeof(SByteConverter);
                    temp[typeof(char)] = typeof(CharConverter);
                    temp[typeof(double)] = typeof(DoubleConverter); 
                    temp[typeof(string)] = typeof(StringConverter);
                    temp[typeof(int)] = typeof(Int32Converter); 
                    temp[typeof(short)] = typeof(Int16Converter); 
                    temp[typeof(long)] = typeof(Int64Converter);
                    temp[typeof(float)] = typeof(SingleConverter); 
                    temp[typeof(UInt16)] = typeof(UInt16Converter);
                    temp[typeof(UInt32)] = typeof(UInt32Converter);
                    temp[typeof(UInt64)] = typeof(UInt64Converter);
                    temp[typeof(object)] = typeof(TypeConverter); 
                    temp[typeof(void)] = typeof(TypeConverter);
                    temp[typeof(CultureInfo)] = typeof(CultureInfoConverter); 
                    temp[typeof(DateTime)] = typeof(DateTimeConverter); 
                    temp[typeof(Decimal)] = typeof(DecimalConverter);
                    temp[typeof(TimeSpan)] = typeof(TimeSpanConverter); 
                    temp[typeof(Guid)] = typeof(GuidConverter);
                    temp[typeof(Array)] = typeof(ArrayConverter);
                    temp[typeof(ICollection)] = typeof(CollectionConverter);
                    temp[typeof(Enum)] = typeof(EnumConverter); 

                    // Special cases for things that are not bound to a specific type 
                    // 
                    temp[_intrinsicReferenceKey] = typeof(ReferenceConverter);
                    temp[_intrinsicNullableKey] = typeof(NullableConverter); 

                    _intrinsicTypeConverters = temp;
                }
                return _intrinsicTypeConverters; 
            }
        } 
 
        /// 
        ///     Adds an editor table for the given editor base type. 
        ///     ypically, editors are specified as metadata on an object. If no metadata for a
        ///     equested editor base type can be found on an object, however, the
        ///     ypeDescriptor will search an editor
        ///     able for the editor type, if one can be found. 
        /// 
        internal static void AddEditorTable(Type editorBaseType, Hashtable table) 
        { 
            if (editorBaseType == null)
            { 
                throw new ArgumentNullException("editorBaseType");
            }

            if (table == null) 
            {
                Debug.Fail("COMPAT: Editor table should not be null"); 
                // don't throw; RTM didn't so we can't do it either. 
            }
 
            lock(_internalSyncObject)
            {
                if (_editorTables == null)
                { 
                    _editorTables = new Hashtable(4);
                } 
 
                if (!_editorTables.ContainsKey(editorBaseType))
                { 
                    _editorTables[editorBaseType] = table;
                }
            }
        } 

        ///  
        ///     CreateInstance implementation.  We delegate to Activator. 
        /// 
        public override object CreateInstance(IServiceProvider provider, Type objectType, Type[] argTypes, object[] args) 
        {
            Debug.Assert(objectType != null, "Should have arg-checked before coming in here");

            object obj = null; 

            if (argTypes != null) 
            { 
                obj = SecurityUtils.SecureConstructorInvoke(objectType, argTypes, args, true, BindingFlags.ExactBinding);
            } 
            else {
                if (args != null) {
                    argTypes = new Type[args.Length];
                    for(int idx = 0; idx < args.Length; idx++) { 
                        if (args[idx] != null) {
                            argTypes[idx] = args[idx].GetType(); 
                        } 
                        else {
                            argTypes[idx] = typeof(object); 
                        }
                    }
                }
                else { 
                    argTypes = new Type[0];
                } 
 
                obj = SecurityUtils.SecureConstructorInvoke(objectType, argTypes, args, true);
            } 

            if (obj == null) {
                obj = SecurityUtils.SecureCreateInstance(objectType, args);
            } 

            return obj; 
        } 

 
        /// 
        ///     Helper method to create editors and type converters. This checks to see if the
        ///     type implements a Type constructor, and if it does it invokes that ctor.
        ///     Otherwise, it just tries to create the type. 
        /// 
        private static object CreateInstance(Type objectType, Type callingType) { 
            object obj = SecurityUtils.SecureConstructorInvoke(objectType, _typeConstructor, new object[] {callingType}, false); 

            if (obj == null) { 
                obj = SecurityUtils.SecureCreateInstance(objectType);
            }

            return obj; 
        }
 
        ///  
        ///     Retrieves custom attributes.
        ///  
        internal AttributeCollection GetAttributes(Type type)
        {
            ReflectedTypeData td = GetTypeData(type, true);
            return td.GetAttributes(); 
        }
 
        ///  
        ///     Our implementation of GetCache sits on top of IDictionaryService.
        ///  
        public override IDictionary GetCache(object instance)
        {
            IComponent comp = instance as IComponent;
            if (comp != null && comp.Site != null) 
            {
                IDictionaryService ds = comp.Site.GetService(typeof(IDictionaryService)) as IDictionaryService; 
                if (ds != null) 
                {
                    IDictionary dict = ds.GetValue(_dictionaryKey) as IDictionary; 
                    if (dict == null)
                    {
                        dict = new Hashtable();
                        ds.SetValue(_dictionaryKey, dict); 
                    }
                    return dict; 
                } 
            }
 
            return null;
        }

        ///  
        ///     Retrieves the class name for our type.
        ///  
        internal string GetClassName(Type type) 
        {
            ReflectedTypeData td = GetTypeData(type, true); 
            return td.GetClassName(null);
        }

        ///  
        ///     Retrieves the component name from the site.
        ///  
        internal string GetComponentName(Type type, object instance) 
        {
            ReflectedTypeData td = GetTypeData(type, true); 
            return td.GetComponentName(instance);
        }

        ///  
        ///     Retrieves the type converter.  If instance is non-null,
        ///     it will be used to retrieve attributes.  Otherwise, _type 
        ///     will be used. 
        /// 
        internal TypeConverter GetConverter(Type type, object instance) 
        {
            ReflectedTypeData td = GetTypeData(type, true);
            return td.GetConverter(instance);
        } 

        ///  
        ///     Return the default event. The default event is determined by the 
        ///     presence of a DefaultEventAttribute on the class.
        ///  
        internal EventDescriptor GetDefaultEvent(Type type, object instance)
        {
            ReflectedTypeData td = GetTypeData(type, true);
            return td.GetDefaultEvent(instance); 
        }
 
        ///  
        ///     Return the default property.
        ///  
        internal PropertyDescriptor GetDefaultProperty(Type type, object instance)
        {
            ReflectedTypeData td = GetTypeData(type, true);
            return td.GetDefaultProperty(instance); 
        }
 
        ///  
        ///     Retrieves the editor for the given base type.
        ///  
        internal object GetEditor(Type type, object instance, Type editorBaseType)
        {
            ReflectedTypeData td = GetTypeData(type, true);
            return td.GetEditor(instance, editorBaseType); 
        }
 
        ///  
        ///      Retrieves a default editor table for the given editor base type.
        ///  
        private static Hashtable GetEditorTable(Type editorBaseType) {

            if (_editorTables == null)
            { 
                lock(_internalSyncObject)
                { 
                    if (_editorTables == null) 
                    {
                        _editorTables = new Hashtable(4); 
                    }
                }
            }
 
            object table = _editorTables[editorBaseType];
 
            if (table == null) 
            {
                // Before we give up, it is possible that the 
                // class initializer for editorBaseType hasn't
                // actually run.
                //
                System.Runtime.CompilerServices.RuntimeHelpers.RunClassConstructor(editorBaseType.TypeHandle); 
                table = _editorTables[editorBaseType];
 
                // If the table is still null, then throw a 
                // sentinel in there so we don't
                // go through this again. 
                //
                if (table == null)
                {
                    lock (_internalSyncObject) 
                    {
                        table = _editorTables[editorBaseType]; 
                        if (table == null) 
                        {
                            _editorTables[editorBaseType] = _editorTables; 
                        }
                    }
                }
            } 

            // Look for our sentinel value that indicates 
            // we have already tried and failed to get 
            // a table.
            // 
            if (table == _editorTables)
            {
                table = null;
            } 

            return (Hashtable)table; 
        } 

        ///  
        ///     Retrieves the events for this type.
        /// 
        internal EventDescriptorCollection GetEvents(Type type)
        { 
            ReflectedTypeData td = GetTypeData(type, true);
            return td.GetEvents(); 
        } 

        ///  
        ///     Retrieves custom extender attributes. We don't support
        ///     extender attributes, so we always return an empty collection.
        /// 
        internal AttributeCollection GetExtendedAttributes(object instance) 
        {
            return AttributeCollection.Empty; 
        } 

        ///  
        ///     Retrieves the class name for our type.
        /// 
        internal string GetExtendedClassName(object instance)
        { 
            return GetClassName(instance.GetType());
        } 
 
        /// 
        ///     Retrieves the component name from the site. 
        /// 
        internal string GetExtendedComponentName(object instance)
        {
            return GetComponentName(instance.GetType(), instance); 
        }
 
        ///  
        ///     Retrieves the type converter.  If instance is non-null,
        ///     it will be used to retrieve attributes.  Otherwise, _type 
        ///     will be used.
        /// 
        internal TypeConverter GetExtendedConverter(object instance)
        { 
            return GetConverter(instance.GetType(), instance);
        } 
 
        /// 
        ///     Return the default event. The default event is determined by the 
        ///     presence of a DefaultEventAttribute on the class.
        /// 
        internal EventDescriptor GetExtendedDefaultEvent(object instance)
        { 
            return null; // we don't support extended events.
        } 
 
        /// 
        ///     Return the default property. 
        /// 
        internal PropertyDescriptor GetExtendedDefaultProperty(object instance)
        {
            return null; // extender properties are never the default. 
        }
 
        ///  
        ///     Retrieves the editor for the given base type.
        ///  
        internal object GetExtendedEditor(object instance, Type editorBaseType)
        {
            return GetEditor(instance.GetType(), instance, editorBaseType);
        } 

        ///  
        ///     Retrieves the events for this type. 
        /// 
        internal EventDescriptorCollection GetExtendedEvents(object instance) 
        {
            return EventDescriptorCollection.Empty;
        }
 
        /// 
        ///     Retrieves the properties for this type. 
        ///  
        internal PropertyDescriptorCollection GetExtendedProperties(object instance)
        { 
            // Is this object a sited component?  If not, then it
            // doesn't have any extender properties.
            //
            Type componentType = instance.GetType(); 
            IComponent component = instance as IComponent;
            if (component == null || component.Site == null) 
            { 
                return PropertyDescriptorCollection.Empty;
            } 

            // Check the component for extender providers.  We prefer
            // IExtenderListService, but will use the container if that's
            // all we have.  In either case, we check the list of extenders 
            // against previously stored data in the object cache.  If
            // the cache is up to date, we just return the extenders in the 
            // cache. 
            //
            IExtenderProvider[] extenders = null; 
            IExtenderListService extenderList = component.Site.GetService(typeof(IExtenderListService)) as IExtenderListService;
            IDictionary cache = TypeDescriptor.GetCache(instance);

            if (extenderList != null) 
            {
                extenders = GetExtenders(extenderList.GetExtenderProviders(), instance, cache); 
            } 
            else
            { 
                IContainer cont = component.Site.Container;
                if (cont != null)
                {
                    extenders = GetExtenders (cont.Components, instance, cache); 
                }
            } 
 
            if (extenders == null)
            { 
                return PropertyDescriptorCollection.Empty;
            }

            // Ok, we have a set of extenders.  Now, check to see if there 
            // are properties already in our object cache.  If there aren't,
            // then we will need to create them. 
            // 
            PropertyDescriptorCollection properties = null;
 
            if (cache != null)
            {
                properties = cache[_extenderPropertiesKey] as PropertyDescriptorCollection;
            } 

            if (properties != null) 
            { 
                return properties;
            } 

            // Unlike normal properties, it is fine for there to be properties with
            // duplicate names here.
            // 
            ArrayList propertyList = null;
 
            for (int idx = 0; idx < extenders.Length; idx++) 
            {
                PropertyDescriptor[] propertyArray = ReflectGetExtendedProperties(extenders[idx]); 

                if (propertyList == null)
                {
                    propertyList = new ArrayList(propertyArray.Length * extenders.Length); 
                }
 
                for (int propIdx = 0; propIdx < propertyArray.Length; propIdx++) 
                {
                    PropertyDescriptor prop = propertyArray[propIdx]; 
                    ExtenderProvidedPropertyAttribute eppa = prop.Attributes[typeof(ExtenderProvidedPropertyAttribute)] as ExtenderProvidedPropertyAttribute;

                    Debug.Assert(eppa != null, "Extender property " + prop.Name + " has no provider attribute.  We will skip it.");
                    if (eppa != null) 
                    {
                        Type receiverType = eppa.ReceiverType; 
                        if (receiverType != null) 
                        {
 
                            if (receiverType.IsAssignableFrom(componentType))
                            {
                                propertyList.Add(prop);
                            } 
                        }
                    } 
                } 
            }
 
            // propertyHash now contains ExtendedPropertyDescriptor objects
            // for each extended property.
            //
            if (propertyList != null) 
            {
                TypeDescriptor.Trace("Extenders : Allocating property collection for {0} properties", propertyList.Count); 
                PropertyDescriptor[] fullArray = new PropertyDescriptor[propertyList.Count]; 
                propertyList.CopyTo(fullArray, 0);
                properties = new PropertyDescriptorCollection(fullArray, true); 
            }
            else
            {
                properties = PropertyDescriptorCollection.Empty; 
            }
 
            if (cache != null) 
            {
                TypeDescriptor.Trace("Extenders : caching extender results"); 
                cache[_extenderPropertiesKey] = properties;
            }

            return properties; 
        }
 
        ///  
        ///     GetExtenders builds a list of extender providers from
        ///     a collection of components.  It validates the extenders 
        ///     against any cached collection of extenders in the
        ///     cache.  If there is a discrepancy, this will erase
        ///     any cached extender properties from the cache and
        ///     save the updated extender list.  If there is no 
        ///     discrepancy this will simply return the cached list.
        ///  
        private static IExtenderProvider[] GetExtenders(ICollection components, object instance, IDictionary cache) 
        {
            bool newExtenders = false; 
            int extenderCount = 0;
            IExtenderProvider[] existingExtenders = null;

            //CanExtend is expensive. We will remember results of CanExtend for the first 64 extenders and using "long canExtend" as a bit vector. 
            // we want to avoid memory allocation as well so we don't use some more sophisticated data structure like an array of booleans
            UInt64 canExtend = 0; 
            int maxCanExtendResults = 64; 
            // currentExtenders is what we intend to return.  If the caller passed us
            // the return value from IExtenderListService, components will already be 
            // an IExtenderProvider[].  If not, then we must treat components as an
            // opaque collection.  We spend a great deal of energy here to avoid
            // copying or allocating memory because this method is called every
            // time a component is asked for its properties. 
            IExtenderProvider[] currentExtenders = components as IExtenderProvider[];
 
            if (cache != null) 
            {
                existingExtenders = cache[_extenderProviderKey] as IExtenderProvider[]; 
            }

            if (existingExtenders == null)
            { 
                newExtenders = true;
            } 
 
            int curIdx = 0;
            int idx = 0; 

            if (currentExtenders != null)
            {
                for (curIdx = 0; curIdx < currentExtenders.Length; curIdx++) 
                {
                    if (currentExtenders[curIdx].CanExtend(instance)) 
                    { 
                        extenderCount++;
                        // Performance:We would like to call CanExtend as little as possible therefore we remember its result 
                        if (curIdx < maxCanExtendResults)
                            canExtend |= (UInt64)1 << curIdx;
                        if (!newExtenders && (idx >= existingExtenders.Length || currentExtenders[curIdx] != existingExtenders[idx++]))
                        { 
                            newExtenders = true;
                        } 
                    } 
                }
            } 
            else if (components != null)
            {
                foreach(object obj in components)
                { 
                    IExtenderProvider prov = obj as IExtenderProvider;
                    if (prov != null && prov.CanExtend(instance)) 
                    { 
                        extenderCount++;
                        if (curIdx < maxCanExtendResults) 
                            canExtend |= (UInt64)1<= existingExtenders.Length || prov != existingExtenders[idx++]))
                        {
                            newExtenders = true; 
                        }
                    } 
                    curIdx++; 
                }
            } 
            if (existingExtenders != null && extenderCount != existingExtenders.Length)
            {
                newExtenders = true;
            } 
            if (newExtenders)
            { 
                TypeDescriptor.Trace("Extenders : object has new extenders : {0}", instance.GetType().Name); 
                TypeDescriptor.Trace("Extenders : Identified {0} extender providers", extenderCount);
                if (currentExtenders == null || extenderCount != currentExtenders.Length) 
                {
                    IExtenderProvider[] newExtenderArray = new IExtenderProvider[extenderCount];

                    curIdx = 0; 
                    idx = 0;
 
                    if (currentExtenders != null && extenderCount > 0) 
                    {
                        while(curIdx < currentExtenders.Length) 
                        {
                            if ((curIdx < maxCanExtendResults && (canExtend & ((UInt64)1 << curIdx)) != 0 )||
                                            (curIdx >= maxCanExtendResults && currentExtenders[curIdx].CanExtend(instance)))
                            { 
                                Debug.Assert(idx < extenderCount, "There are more extenders than we expect");
                                newExtenderArray[idx++] = currentExtenders[curIdx]; 
                            } 
                            curIdx++;
                        } 
                        Debug.Assert(idx == extenderCount, "Wrong number of extenders");
                    }
                    else if (extenderCount > 0)
                    { 
                        IEnumerator componentEnum = components.GetEnumerator();
                        while(componentEnum.MoveNext()) 
                        { 
                            IExtenderProvider p = componentEnum.Current as IExtenderProvider;
 
                            if (p != null && ((curIdx < maxCanExtendResults && (canExtend & ((UInt64)1 << curIdx)) != 0) ||
                                                (curIdx >= maxCanExtendResults && p.CanExtend(instance))))
                            {
                                Debug.Assert(idx < extenderCount, "There are more extenders than we expect"); 
                                newExtenderArray[idx++] = p;
                            } 
                            curIdx++; 
                        }
                        Debug.Assert(idx == extenderCount, "Wrong number of extenders"); 
                    }
                    currentExtenders = newExtenderArray;
                }
 
                if (cache != null)
                { 
                    TypeDescriptor.Trace("Extenders : caching extender provider results"); 
                    cache[_extenderProviderKey] = currentExtenders;
                    cache.Remove(_extenderPropertiesKey); 
                }
            }
            else
            { 
                currentExtenders = existingExtenders;
            } 
            return currentExtenders; 
        }
 
        /// 
        ///     Retrieves the owner for a property.
        /// 
        internal object GetExtendedPropertyOwner(object instance, PropertyDescriptor pd) 
        {
            return GetPropertyOwner(instance.GetType(), instance, pd); 
        } 

        ////////////////////////////////////////////////////////// 
        /// 
        ///     Provides a type descriptor for the given object.  We only support this
        ///     if the object is a component that
        ///  
        public override ICustomTypeDescriptor GetExtendedTypeDescriptor(object instance)
        { 
            Debug.Fail("This should never be invoked.  TypeDescriptionNode should wrap for us."); 
            return null;
        } 

        /// 
        ///     The name of the specified component, or null if the component has no name.
        ///     In many cases this will return the same value as GetComponentName. If the 
        ///     component resides in a nested container or has other nested semantics, it may
        ///     return a different fully qualfied name. 
        /// 
        ///     If not overridden, the default implementation of this method will call
        ///     GetComponentName. 
        /// 
        public override string GetFullComponentName(object component) {
            IComponent comp = component as IComponent;
            if (comp != null) { 
                INestedSite ns = comp.Site as INestedSite;
                if (ns != null) { 
                    return ns.FullName; 
                }
            } 

            return TypeDescriptor.GetComponentName(component);
        }
 
        /// 
        ///     Returns an array of types we have populated metadata for that live 
        ///     in the current module. 
        /// 
        internal Type[] GetPopulatedTypes(Module module) { 
            ArrayList typeList = new ArrayList();;

            foreach(DictionaryEntry de in _typeData) {
                Type type = (Type)de.Key; 
                ReflectedTypeData typeData = (ReflectedTypeData)de.Value;
 
                if (type.Module == module && typeData.IsPopulated) { 
                    typeList.Add(type);
                } 
            }

            return (Type[])typeList.ToArray(typeof(Type));
        } 

        ///  
        ///     Retrieves the properties for this type. 
        /// 
        internal PropertyDescriptorCollection GetProperties(Type type) 
        {
            ReflectedTypeData td = GetTypeData(type, true);
            return td.GetProperties();
        } 

        ///  
        ///     Retrieves the owner for a property. 
        /// 
        internal object GetPropertyOwner(Type type, object instance, PropertyDescriptor pd) 
        {
            return TypeDescriptor.GetAssociation(type, instance);
        }
 
        /// 
        ///     Returns an Type for the given type.  Since type implements IReflect, 
        ///     we just return objectType. 
        /// 
        public override Type GetReflectionType(Type objectType, object instance) 
        {
            Debug.Assert(objectType != null, "Should have arg-checked before coming in here");
            return objectType;
        } 

        ///  
        ///     Returns the type data for the given type, or 
        ///     null if there is no type data for the type yet and
        ///     createIfNeeded is false. 
        /// 
        private ReflectedTypeData GetTypeData(Type type, bool createIfNeeded) {

            ReflectedTypeData td = null; 

            if (_typeData != null) { 
                td = (ReflectedTypeData)_typeData[type]; 
                if (td != null) {
                    return td; 
                }
            }

            lock (_internalSyncObject) { 
                if (_typeData != null) {
                    td = (ReflectedTypeData)_typeData[type]; 
                } 

                if (td == null && createIfNeeded) { 
                    td = new ReflectedTypeData(type);
                    if (_typeData == null) {
                        _typeData = new Hashtable();
                    } 
                    _typeData[type] = td;
                } 
            } 

            return td; 
        }

        /// 
        ///     This method returns a custom type descriptor for the given type / object. 
        ///     The objectType parameter is always valid, but the instance parameter may
        ///     be null if no instance was passed to TypeDescriptor.  The method should 
        ///     return a custom type descriptor for the object.  If the method is not 
        ///     interested in providing type information for the object it should
        ///     return null. 
        /// 
        public override ICustomTypeDescriptor GetTypeDescriptor(Type objectType, object instance)
        {
            Debug.Fail("This should never be invoked.  TypeDescriptionNode should wrap for us."); 
            return null;
        } 
 
        /// 
        ///     Retrieves a type from a name. 
        /// 
        private static Type GetTypeFromName(string typeName)
        {
            Type t = Type.GetType(typeName); 

            if (t == null) 
            { 
                int commaIndex = typeName.IndexOf(',');
 
                if (commaIndex != -1)
                {
                    // At design time, it's possible for us to reuse
                    // an assembly but add new types.  The app domain 
                    // will cache the assembly based on identity, however,
                    // so it could be looking in the previous version 
                    // of the assembly and not finding the type.  We work 
                    // around this by looking for the non-assembly qualified
                    // name, which causes the domain to raise a type 
                    // resolve event.
                    //
                    t = Type.GetType(typeName.Substring(0, commaIndex));
                } 
            }
 
            return t; 
        }
 
        /// 
        ///     This method returns true if the data cache in this reflection
        ///     type descriptor has data in it.
        ///  
        internal bool IsPopulated(Type type)
        { 
            ReflectedTypeData td = GetTypeData(type, false); 
            if (td != null) {
                return td.IsPopulated; 
            }
            return false;
        }
 
        /// 
        ///     Static helper API around reflection to get and cache 
        ///     custom attributes.  This does not recurse, but it will 
        ///     walk interfaces on the type.  Interfaces are added
        ///     to the end, so merging should be done from length - 1 
        ///     to 0.
        /// 
        private static Attribute[] ReflectGetAttributes(Type type)
        { 
            if (_attributeCache == null)
            { 
                lock (_internalSyncObject) 
                {
                    if (_attributeCache == null) 
                    {
                        _attributeCache = new Hashtable();
                    }
                } 
            }
 
            Attribute[] attrs = (Attribute[])_attributeCache[type]; 
            if (attrs == null)
            { 
                TypeDescriptor.Trace("Attributes : Building attributes for {0}", type.Name);

                // Get the type's attributes.
                // 
                object[] typeAttrs = type.GetCustomAttributes(typeof(Attribute), false);
 
                attrs = new Attribute[typeAttrs.Length]; 
                typeAttrs.CopyTo(attrs, 0);
 
                _attributeCache[type] = attrs;
            }

            return attrs; 
        }
 
        ///  
        ///     Static helper API around reflection to get and cache
        ///     custom attributes.  This does not recurse to the base class. 
        /// 
        internal static Attribute[] ReflectGetAttributes(MemberInfo member)
        {
            if (_attributeCache == null) 
            {
                lock (_internalSyncObject) 
                { 
                    if (_attributeCache == null)
                    { 
                        _attributeCache = new Hashtable();
                    }
                }
            } 

            Attribute[] attrs = (Attribute[])_attributeCache[member]; 
            if (attrs == null) 
            {
                // Get the member's attributes. 
                //
                object[] memberAttrs = member.GetCustomAttributes(typeof(Attribute), false);
                attrs = new Attribute[memberAttrs.Length];
                memberAttrs.CopyTo(attrs, 0); 
                _attributeCache[member] = attrs;
            } 
 
            return attrs;
        } 

        /// 
        ///     Static helper API around reflection to get and cache
        ///     events.  This does not recurse to the base class. 
        /// 
        private static EventDescriptor[] ReflectGetEvents(Type type) 
        { 
            if (_eventCache == null)
            { 
                lock (_internalSyncObject)
                {
                    if (_eventCache == null)
                    { 
                        _eventCache = new Hashtable();
                    } 
                } 
            }
 
            EventDescriptor[] events = (EventDescriptor[])_eventCache[type];
            if (events == null)
            {
                BindingFlags bindingFlags = BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.Instance; 
                TypeDescriptor.Trace("Events : Building events for {0}", type.Name);
 
                // Get the type's events.  Events may have their add and 
                // remove methods individually overridden in a derived
                // class, but at some point in the base class chain both 
                // methods must exist.  If we find an event that doesn't
                // have both add and remove, we skip it here, because it
                // will be picked up in our base class scan.
                // 
                EventInfo[] eventInfos = type.GetEvents(bindingFlags);
                events = new EventDescriptor[eventInfos.Length]; 
                int eventCount = 0; 

                for (int idx = 0; idx < eventInfos.Length; idx++) 
                {
                    EventInfo eventInfo = eventInfos[idx];

                    // GetEvents returns events that are on nonpublic types 
                    // if those types are from our assembly.  Screen these.
                    // 
                    if ((!(eventInfo.DeclaringType.IsPublic || eventInfo.DeclaringType.IsNestedPublic)) && (eventInfo.DeclaringType.Assembly == typeof(ReflectTypeDescriptionProvider).Assembly)) { 
                        Debug.Fail("Hey, assumption holds true.  Rip this assert.");
                        continue; 
                    }

                    MethodInfo addMethod = eventInfo.GetAddMethod();
                    MethodInfo removeMethod = eventInfo.GetRemoveMethod(); 

                    if (addMethod != null && removeMethod != null) 
                    { 
                        events[eventCount++] = new ReflectEventDescriptor(type, eventInfo);
                    } 
                }

                if (eventCount != events.Length)
                { 
                    EventDescriptor[] newEvents = new EventDescriptor[eventCount];
                    Array.Copy(events, 0, newEvents, 0, eventCount); 
                    events = newEvents; 
                }
 
                #if DEBUG
                foreach(EventDescriptor dbgEvent in events)
                {
                    Debug.Assert(dbgEvent != null, "Holes in event array for type " + type); 
                }
                #endif 
                _eventCache[type] = events; 
            }
 
            return events;
        }

        ///  
        ///     This performs the actual reflection needed to discover
        ///     extender properties.  If object caching is supported this 
        ///     will maintain a cache of property descriptors on the 
        ///     extender provider.  Extender properties are actually two
        ///     property descriptors in one.  There is a chunk of per-class 
        ///     data in a ReflectPropertyDescriptor that defines the
        ///     parameter types and get and set methods of the extended property,
        ///     and there is an ExtendedPropertyDescriptor that combines this
        ///     with an extender provider object to create what looks like a 
        ///     normal property.  ReflectGetExtendedProperties maintains two
        ///     separate caches for these two sets:  a static one for the 
        ///     ReflectPropertyDescriptor values that don't change for each 
        ///     provider instance, and a per-provider cache that contains
        ///     the ExtendedPropertyDescriptors. 
        /// 
        private static PropertyDescriptor[] ReflectGetExtendedProperties(IExtenderProvider provider)
        {
            IDictionary cache = TypeDescriptor.GetCache(provider); 
            PropertyDescriptor[] properties;
 
            if (cache != null) 
            {
                properties = cache[_extenderProviderPropertiesKey] as PropertyDescriptor[]; 
                if (properties != null)
                {
                    return properties;
                } 
            }
 
            // Our per-instance cache missed.  We have never seen this instance of the 
            // extender provider before.  See if we can find our class-based
            // property store. 
            //
            if (_extendedPropertyCache == null)
            {
                lock (_internalSyncObject) 
                {
                    if (_extendedPropertyCache == null) 
                    { 
                        _extendedPropertyCache = new Hashtable();
                    } 
                }
            }

            Type providerType = provider.GetType(); 
            ReflectPropertyDescriptor[] extendedProperties = (ReflectPropertyDescriptor[])_extendedPropertyCache[providerType];
 
            // Our class-based property store failed as well, so we need to build up the set of 
            // extended properties here.
            // 
            if (extendedProperties == null)
            {
                AttributeCollection attributes = TypeDescriptor.GetAttributes(providerType);
                ArrayList extendedList = new ArrayList(attributes.Count); 

                foreach(Attribute attr in attributes) 
                { 
                    ProvidePropertyAttribute provideAttr = attr as ProvidePropertyAttribute;
 
                    if (provideAttr != null)
                    {
                        Type receiverType = GetTypeFromName(provideAttr.ReceiverTypeName);
 
                        if (receiverType != null)
                        { 
                            MethodInfo getMethod = providerType.GetMethod("Get" + provideAttr.PropertyName, new Type[] {receiverType}); 

                            if (getMethod != null && !getMethod.IsStatic && getMethod.IsPublic) 
                            {
                                MethodInfo setMethod = providerType.GetMethod("Set" + provideAttr.PropertyName, new Type[] {receiverType, getMethod.ReturnType});

                                if (setMethod != null && (setMethod.IsStatic || !setMethod.IsPublic)) 
                                {
                                    setMethod = null; 
                                } 

                                extendedList.Add(new ReflectPropertyDescriptor(providerType, provideAttr.PropertyName, getMethod.ReturnType, receiverType, getMethod, setMethod, null)); 
                            }
                        }
                    }
                } 

                extendedProperties = new ReflectPropertyDescriptor[extendedList.Count]; 
                extendedList.CopyTo(extendedProperties, 0); 
                _extendedPropertyCache[providerType] = extendedProperties;
            } 

            // Now that we have our extended properties we can build up a list of callable properties.  These can be
            // returned to the user.
            // 
            properties = new PropertyDescriptor[extendedProperties.Length];
            for (int idx = 0; idx < extendedProperties.Length; idx++) 
            { 
                Attribute[] attrs = null;
                IComponent comp = provider as IComponent; 
                if (comp == null || comp.Site == null)
                {
                    attrs = new Attribute[] {DesignOnlyAttribute.Yes};
                } 

                ReflectPropertyDescriptor  rpd = extendedProperties[idx]; 
                ExtendedPropertyDescriptor epd = new ExtendedPropertyDescriptor(rpd, rpd.ExtenderGetReceiverType(), provider, attrs); 
                properties[idx] = epd;
            } 

            if (cache != null)
            {
                cache[_extenderProviderPropertiesKey] = properties; 
            }
 
            return properties; 
        }
 
        /// 
        ///     Static helper API around reflection to get and cache
        ///     properties. This does not recurse to the base class.
        ///  
        private static PropertyDescriptor[] ReflectGetProperties(Type type)
        { 
            if (_propertyCache == null) 
            {
                lock(_internalSyncObject) 
                {
                    if (_propertyCache == null)
                    {
                        _propertyCache = new Hashtable(); 
                    }
                } 
            } 

            PropertyDescriptor[] properties = (PropertyDescriptor[])_propertyCache[type]; 
            if (properties == null)
            {
                BindingFlags bindingFlags = BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.Instance;
                TypeDescriptor.Trace("Properties : Building properties for {0}", type.Name); 

                // Get the type's properties.  Properties may have their 
                // get and set methods individually overridden in a derived 
                // class, so if we find a missing method we need to walk
                // down the base class chain to find it.  We actually merge 
                // "new" properties of the same name, so we must preserve
                // the member info for each method individually.
                //
                PropertyInfo[] propertyInfos = type.GetProperties(bindingFlags); 
                properties = new PropertyDescriptor[propertyInfos.Length];
                int propertyCount = 0; 
 

                for (int idx = 0; idx < propertyInfos.Length; idx++) 
                {
                    PropertyInfo propertyInfo = propertyInfos[idx];

                    // Today we do not support parameterized properties. 
                    //
                    if (propertyInfo.GetIndexParameters().Length > 0) { 
                        continue; 
                    }
 
                    MethodInfo getMethod = propertyInfo.GetGetMethod();
                    MethodInfo setMethod = propertyInfo.GetSetMethod();
                    string name = propertyInfo.Name;
 
                    // If the property only overrode "set", then we don't
                    // pick it up here.  Rather, we just merge it in from 
                    // the base class list. 

 
                    // If a property had at least a get method, we consider it.  We don't
                    // consider write-only properties.
                    //
                    if (getMethod != null) 
                    {
                        properties[propertyCount++] = new ReflectPropertyDescriptor(type, name, 
                                                                                    propertyInfo.PropertyType, 
                                                                                    propertyInfo, getMethod,
                                                                                    setMethod, null); 
                    }
                }

 
                if (propertyCount != properties.Length)
                { 
                    PropertyDescriptor[] newProperties = new PropertyDescriptor[propertyCount]; 
                    Array.Copy(properties, 0, newProperties, 0, propertyCount);
                    properties = newProperties; 
                }

                #if DEBUG
                foreach(PropertyDescriptor dbgProp in properties) 
                {
                    Debug.Assert(dbgProp != null, "Holes in property array for type " + type); 
                } 
                #endif
                _propertyCache[type] = properties; 
            }

            return properties;
        } 

        ///  
        ///     Refreshes the contents of this type descriptor.  This does not 
        ///     actually requery, but it will clear our state so the next
        ///     query re-populates. 
        /// 
        internal void Refresh(Type type)
        {
            ReflectedTypeData td = GetTypeData(type, false); 
            if (td != null) {
                td.Refresh(); 
            } 
        }
 
        /// 
        ///      Searches the provided intrinsic hashtable for a match with the object type.
        ///      At the beginning, the hashtable contains types for the various converters.
        ///      As this table is searched, the types for these objects 
        ///      are replaced with instances, so we only create as needed.  This method
        ///      does the search up the base class hierarchy and will create instances 
        ///      for types as needed.  These instances are stored back into the table 
        ///      for the base type, and for the original component type, for fast access.
        ///  
        private static object SearchIntrinsicTable(Hashtable table, Type callingType)
        {
            object hashEntry = null;
 
            // We take a lock on this table.  Nothing in this code calls out to
            // other methods that lock, so it should be fairly safe to grab this 
            // lock.  Also, this allows multiple intrinsic tables to be searched 
            // at once.
            // 
            lock(table)
            {
                Type baseType = callingType;
                while (baseType != null && baseType != typeof(object)) 
                {
                    hashEntry = table[baseType]; 
 
                    // If the entry is a late-bound type, then try to
                    // resolve it. 
                    //
                    string typeString = hashEntry as string;
                    if (typeString != null)
                    { 
                        hashEntry = Type.GetType(typeString);
                        if (hashEntry != null) 
                        { 
                            table[baseType] = hashEntry;
                        } 
                    }

                    if (hashEntry != null)
                    { 
                        break;
                    } 
 
                    baseType = baseType.BaseType;
                } 

                // Now make a scan through each value in the table, looking for interfaces.
                // If we find one, see if the object implements the interface.
                // 
                if (hashEntry == null)
                { 
 
                    foreach(DictionaryEntry de in table)
                    { 
                        Type keyType = de.Key as Type;

                        if (keyType != null && keyType.IsInterface && keyType.IsAssignableFrom(callingType))
                        { 

                            hashEntry = de.Value; 
                            string typeString = hashEntry as string; 

                            if (typeString != null) 
                            {
                                hashEntry = Type.GetType(typeString);
                                if (hashEntry != null)
                                { 
                                    table[callingType] = hashEntry;
                                } 
                            } 

                            if (hashEntry != null) 
                            {
                                break;
                            }
                        } 
                    }
                } 
 
                // Special case converters
                // 
                if (hashEntry == null)
                {
                    if (callingType.IsGenericType && callingType.GetGenericTypeDefinition() == typeof(Nullable<>))
                    { 
                        // Check if it is a nullable value
                        hashEntry = table[_intrinsicNullableKey]; 
                    } 
                    else if (callingType.IsInterface)
                    { 
                        // Finally, check to see if the component type is some unknown interface.
                        // We have a custom converter for that.
                        hashEntry = table[_intrinsicReferenceKey];
                    } 
                }
 
                // Interfaces do not derive from object, so we 
                // must handle the case of no hash entry here.
                // 
                if (hashEntry == null)
                {
                    hashEntry = table[typeof(object)];
                } 

                // If the entry is a type, create an instance of it and then 
                // replace the entry.  This way we only need to create once. 
                // We can only do this if the object doesn't want a type
                // in its constructor. 
                //
                Type type = hashEntry as Type;

                if (type != null) 
                {
                    hashEntry = CreateInstance(type, callingType); 
                    if (type.GetConstructor(_typeConstructor) == null) 
                    {
                        table[callingType] = hashEntry; 
                    }
                }
            }
 
            return hashEntry;
        } 
 
        /// 
        ///     This class contains all the reflection information for a 
        ///     given type.
        /// 
        private class ReflectedTypeData {
 
            private Type                            _type;
            private AttributeCollection             _attributes; 
            private EventDescriptorCollection       _events; 
            private PropertyDescriptorCollection    _properties;
            private TypeConverter                   _converter; 
            private object[]                        _editors;
            private Type[]                          _editorTypes;
            private int                             _editorCount;
 
            internal ReflectedTypeData(Type type) {
                _type = type; 
                TypeDescriptor.Trace("Reflect : Creating ReflectedTypeData for {0}", type.Name); 
            }
 
            /// 
            ///     This method returns true if the data cache in this reflection
            ///     type descriptor has data in it.
            ///  
            internal bool IsPopulated
            { 
                get 
                {
                    return (_attributes != null) | (_events != null) | (_properties != null); 
                }
            }

            ///  
            ///     Retrieves custom attributes.
            ///  
            internal AttributeCollection GetAttributes() 
            {
                // Worst case collision scenario:  we don't want the perf hit 
                // of taking a lock, so if we collide we will query for
                // attributes twice.  Not a big deal.
                //
                if (_attributes == null) 
                {
                    TypeDescriptor.Trace("Attributes : Building collection for {0}", _type.Name); 
 
                    // Obtaining attributes follows a very critical order: we must take care that
                    // we merge attributes the right way.  Consider this: 
                    //
                    // [A4]
                    // interface IBase;
                    // 
                    // [A3]
                    // interface IDerived; 
                    // 
                    // [A2]
                    // class Base : IBase; 
                    //
                    // [A1]
                    // class Derived : Base, IDerived
                    // 
                    // Calling GetAttributes on type Derived must merge attributes in the following
                    // order:  A1 - A4.  Interfaces always lose to types, and interfaces and types 
                    // must be merged in the same order.  At the same time, we must be careful 
                    // that we don't always go through reflection here, because someone could have
                    // created a custom provider for a type.  Because there is only one instance 
                    // of ReflectTypeDescriptionProvider created for typeof(object), if our code
                    // is invoked here we can be sure that there is no custom provider for
                    // _type all the way up the base class chain.
                    // We cannot be sure that there is no custom provider for 
                    // interfaces that _type implements, however, because they are not derived
                    // from _type.  So, for interfaces, we must go through TypeDescriptor 
                    // again to get the interfaces attributes. 

                    // Get the type's attributes. This does not recurse up the base class chain. 
                    // We append base class attributes to this array so when walking we will
                    // walk from Length - 1 to zero.
                    //
                    Attribute[] attrArray = ReflectTypeDescriptionProvider.ReflectGetAttributes(_type); 
                    Type baseType = _type.BaseType;
 
                    while (baseType != null && baseType != typeof(object)) 
                    {
                        Attribute[] baseArray = ReflectTypeDescriptionProvider.ReflectGetAttributes(baseType); 
                        Attribute[] temp = new Attribute[attrArray.Length + baseArray.Length];
                        Array.Copy(attrArray, 0, temp, 0, attrArray.Length);
                        Array.Copy(baseArray, 0, temp, attrArray.Length, baseArray.Length);
                        attrArray = temp; 
                        baseType = baseType.BaseType;
                    } 
 
                    // Next, walk the type's interfaces.  We append these to
                    // the attribute array as well. 
                    //
                    int ifaceStartIdx = attrArray.Length;
                    Type[] interfaces = _type.GetInterfaces();
                    TypeDescriptor.Trace("Attributes : Walking {0} interfaces", interfaces.Length); 
                    for(int idx = 0; idx < interfaces.Length; idx++)
                    { 
                        Type iface = interfaces[idx]; 

                        // only do this for public interfaces. 
                        //
                        if ((iface.Attributes & (TypeAttributes.Public | TypeAttributes.NestedPublic)) != 0) {
                            // No need to pass an instance into GetTypeDescriptor here because, if someone provided a custom
                            // provider based on object, it already would have hit. 
                            AttributeCollection ifaceAttrs = TypeDescriptor.GetAttributes(iface);
                            if (ifaceAttrs.Count > 0) { 
                                Attribute[] temp = new Attribute[attrArray.Length + ifaceAttrs.Count]; 
                                Array.Copy(attrArray, 0, temp, 0, attrArray.Length);
                                ifaceAttrs.CopyTo(temp, attrArray.Length); 
                                attrArray = temp;
                            }
                        }
                    } 

                    // Finally, hash all these attributes up in reverse order. 
                    // 
                    Hashtable attributeHash = new Hashtable(attrArray.Length);
 
                    for (int idx = attrArray.Length -1; idx >= 0; idx--)
                    {
                        bool addAttr = true;
                        if (idx >= ifaceStartIdx) { 
                            for (int ifaceSkipIdx = 0; ifaceSkipIdx < _skipInterfaceAttributeList.Length; ifaceSkipIdx++)
                            { 
                                if (_skipInterfaceAttributeList[ifaceSkipIdx].IsInstanceOfType(attrArray[idx])) 
                                {
                                    addAttr = false; 
                                    break;
                                }
                            }
 
                        }
 
                        if (addAttr) { 
                            attributeHash[attrArray[idx].TypeId] = attrArray[idx];
                        } 
                    }

                    attrArray = new Attribute[attributeHash.Count];
                    attributeHash.Values.CopyTo(attrArray, 0); 
                    _attributes = new AttributeCollection(attrArray);
                } 
 
                return _attributes;
            } 

            /// 
            ///     Retrieves the class name for our type.
            ///  
            internal string GetClassName(object instance)
            { 
                return _type.FullName; 
            }
 
            /// 
            ///     Retrieves the component name from the site.
            /// 
            internal string GetComponentName(object instance) 
            {
                IComponent comp = instance as IComponent; 
                if (comp != null) 
                {
                    ISite site = comp.Site; 
                    if (site != null)
                    {
                        INestedSite nestedSite = site as INestedSite;
                        if (nestedSite != null) 
                        {
                            return nestedSite.FullName; 
                        } 
                        else
                        { 
                            return site.Name;
                        }
                    }
                } 

                return null; 
            } 

            ///  
            ///     Retrieves the type converter.  If instance is non-null,
            ///     it will be used to retrieve attributes.  Otherwise, _type
            ///     will be used.
            ///  
            internal TypeConverter GetConverter(object instance)
            { 
                TypeConverterAttribute typeAttr = null; 

                // For instances, the design time object for them may want to redefine the 
                // attributes.  So, we search the attribute here based on the instance.  If found,
                // we then search on the same attribute based on type.  If the two don't match, then
                // we cannot cache the value and must re-create every time.  It is rare for a designer
                // to override these attributes, so we want to be smart here. 
                //
                if (instance != null) 
                { 
                    typeAttr = (TypeConverterAttribute)TypeDescriptor.GetAttributes(_type)[typeof(TypeConverterAttribute)];
                    TypeConverterAttribute instanceAttr = (TypeConverterAttribute)TypeDescriptor.GetAttributes(instance)[typeof(TypeConverterAttribute)]; 
                    if (typeAttr != instanceAttr)
                    {
                        Type converterType = GetTypeFromName(instanceAttr.ConverterTypeName);
                        if (converterType != null && typeof(TypeConverter).IsAssignableFrom(converterType)) 
                        {
                            try { 
                                IntSecurity.FullReflection.Assert(); 
                                return (TypeConverter)ReflectTypeDescriptionProvider.CreateInstance(converterType, _type);
                            } finally { 
                                CodeAccessPermission.RevertAssert();
                            }
                        }
                    } 
                }
 
                // If we got here, we return our type-based converter. 
                //
                if (_converter == null) 
                {
                    TypeDescriptor.Trace("Converters : Building converter for {0}", _type.Name);

                    if (typeAttr == null) 
                    {
                        typeAttr = (TypeConverterAttribute)TypeDescriptor.GetAttributes(_type)[typeof(TypeConverterAttribute)]; 
                    } 

                    if (typeAttr != null) 
                    {
                        Type converterType = GetTypeFromName(typeAttr.ConverterTypeName);
                        if (converterType != null && typeof(TypeConverter).IsAssignableFrom(converterType))
                        { 
                            try {
                                IntSecurity.FullReflection.Assert(); 
                                _converter = (TypeConverter)ReflectTypeDescriptionProvider.CreateInstance(converterType, _type); 
                            } finally {
                                CodeAccessPermission.RevertAssert(); 
                            }
                        }
                    }
 
                    if (_converter == null)
                    { 
                        // We did not get a converter.  Traverse up the base class chain until 
                        // we find one in the stock hashtable.
                        // 
                        _converter = (TypeConverter)ReflectTypeDescriptionProvider.SearchIntrinsicTable(IntrinsicTypeConverters, _type);
                        Debug.Assert(_converter != null, "There is no intrinsic setup in the hashtable for the Object type");
                    }
                } 

                return _converter; 
            } 

            ///  
            ///     Return the default event. The default event is determined by the
            ///     presence of a DefaultEventAttribute on the class.
            /// 
            internal EventDescriptor GetDefaultEvent(object instance) 
            {
                AttributeCollection attributes; 
 
                if (instance != null)
                { 
                    attributes = TypeDescriptor.GetAttributes(instance);
                }
                else
                { 
                    attributes = TypeDescriptor.GetAttributes(_type);
                } 
 
                DefaultEventAttribute attr = (DefaultEventAttribute)attributes[typeof(DefaultEventAttribute)];
                if (attr != null && attr.Name != null) 
                {
                    if (instance != null)
                    {
                        return TypeDescriptor.GetEvents(instance)[attr.Name]; 
                    }
                    else 
                    { 
                        return TypeDescriptor.GetEvents(_type)[attr.Name];
                    } 
                }

                return null;
            } 

            ///  
            ///     Return the default property. 
            /// 
            internal PropertyDescriptor GetDefaultProperty(object instance) 
            {
                AttributeCollection attributes;

                if (instance != null) 
                {
                    attributes = TypeDescriptor.GetAttributes(instance); 
                } 
                else
                { 
                    attributes = TypeDescriptor.GetAttributes(_type);
                }

                DefaultPropertyAttribute attr = (DefaultPropertyAttribute)attributes[typeof(DefaultPropertyAttribute)]; 
                if (attr != null && attr.Name != null)
                { 
                    if (instance != null) 
                    {
                        return TypeDescriptor.GetProperties(instance)[attr.Name]; 
                    }
                    else
                    {
                        return TypeDescriptor.GetProperties(_type)[attr.Name]; 
                    }
                } 
 
                return null;
            } 

            /// 
            ///     Retrieves the editor for the given base type.
            ///  
            internal object GetEditor(object instance, Type editorBaseType)
            { 
                EditorAttribute typeAttr; 

                // For instances, the design time object for them may want to redefine the 
                // attributes.  So, we search the attribute here based on the instance.  If found,
                // we then search on the same attribute based on type.  If the two don't match, then
                // we cannot cache the value and must re-create every time.  It is rare for a designer
                // to override these attributes, so we want to be smart here. 
                //
                if (instance != null) 
                { 
                    typeAttr = GetEditorAttribute(TypeDescriptor.GetAttributes(_type), editorBaseType);
                    EditorAttribute instanceAttr = GetEditorAttribute(TypeDescriptor.GetAttributes(instance), editorBaseType); 
                    if (typeAttr != instanceAttr)
                    {
                        Type editorType = GetTypeFromName(instanceAttr.EditorTypeName);
                        if (editorType != null && editorBaseType.IsAssignableFrom(editorType)) 
                        {
                            return ReflectTypeDescriptionProvider.CreateInstance(editorType, _type); 
                        } 
                    }
                } 

                // If we got here, we return our type-based editor.
                //
                lock(this) 
                {
                    for (int idx = 0; idx < _editorCount; idx++) 
                    { 
                        if (_editorTypes[idx] == editorBaseType)
                        { 
                            return _editors[idx];
                        }
                    }
                } 

                // Editor is not cached yet.  Look in the attributes. 
                // 
                object editor = null;
 
                typeAttr = GetEditorAttribute(TypeDescriptor.GetAttributes(_type), editorBaseType);
                if (typeAttr != null)
                {
                    Type editorType = GetTypeFromName(typeAttr.EditorTypeName); 
                    if (editorType != null && editorBaseType.IsAssignableFrom(editorType))
                    { 
                        editor = ReflectTypeDescriptionProvider.CreateInstance(editorType, _type); 
                    }
                } 

                // Editor is not in the attributes.  Search intrinsic tables.
                //
                if (editor == null) 
                {
                    Hashtable intrinsicEditors = ReflectTypeDescriptionProvider.GetEditorTable(editorBaseType); 
                    if (intrinsicEditors != null) 
                    {
                        editor = ReflectTypeDescriptionProvider.SearchIntrinsicTable(intrinsicEditors, _type); 
                    }

                    // As a quick sanity check, check to see that the editor we got back is of
                    // the correct type. 
                    //
                    if (editor != null && !editorBaseType.IsInstanceOfType(editor)) { 
                        Debug.Fail("Editor " + editor.GetType().FullName + " is not an instance of " + editorBaseType.FullName + " but it is in that base types table."); 
                        editor = null;
                    } 
                }

                if (editor != null)
                { 
                    lock(this)
                    { 
                        if (_editorTypes == null || _editorTypes.Length == _editorCount) 
                        {
                            int newLength = (_editorTypes == null ? 4 : _editorTypes.Length * 2); 

                            Type[] newTypes = new Type[newLength];
                            object[] newEditors = new object[newLength];
 
                            if (_editorTypes != null)
                            { 
                                _editorTypes.CopyTo(newTypes, 0); 
                                _editors.CopyTo(newEditors, 0);
                            } 

                            _editorTypes = newTypes;
                            _editors = newEditors;
 
                            _editorTypes[_editorCount] = editorBaseType;
                            _editors[_editorCount++] = editor; 
                        } 
                    }
                } 

                return editor;
            }
 
            /// 
            ///     Helper method to return an editor attribute of the correct base type. 
            ///  
            private static EditorAttribute GetEditorAttribute(AttributeCollection attributes, Type editorBaseType)
            { 
                foreach(Attribute attr in attributes)
                {
                    EditorAttribute edAttr = attr as EditorAttribute;
                    if (edAttr != null) 
                    {
                        Type attrEditorBaseType = Type.GetType(edAttr.EditorBaseTypeName); 
 
                        if (attrEditorBaseType != null && attrEditorBaseType == editorBaseType)
                        { 
                            return edAttr;
                        }
                    }
                } 

                return null; 
            } 

            ///  
            ///     Retrieves the events for this type.
            /// 
            internal EventDescriptorCollection GetEvents()
            { 
                // Worst case collision scenario:  we don't want the perf hit
                // of taking a lock, so if we collide we will query for 
                // events twice.  Not a big deal. 
                //
                if (_events == null) 
                {
                    TypeDescriptor.Trace("Events : Building collection for {0}", _type.Name);

                    EventDescriptor[] eventArray; 
                    Dictionary eventList = new Dictionary(16);
                    Type baseType = _type; 
                    Type objType = typeof(object); 

                    do { 
                        eventArray = ReflectGetEvents(baseType);
                        foreach(EventDescriptor ed in eventArray) {
                            if (!eventList.ContainsKey(ed.Name)) {
                                eventList.Add(ed.Name, ed); 
                            }
                        } 
                        baseType = baseType.BaseType; 
                    }
                    while(baseType != null && baseType != objType); 

                    eventArray = new EventDescriptor[eventList.Count];
                    eventList.Values.CopyTo(eventArray, 0);
                    _events = new EventDescriptorCollection(eventArray, true); 
                }
 
                return _events; 
            }
 
            /// 
            ///     Retrieves the properties for this type.
            /// 
            internal PropertyDescriptorCollection GetProperties() 
            {
                // Worst case collision scenario:  we don't want the perf hit 
                // of taking a lock, so if we collide we will query for 
                // properties twice.  Not a big deal.
                // 
                if (_properties == null)
                {
                    TypeDescriptor.Trace("Properties : Building collection for {0}", _type.Name);
 
                    PropertyDescriptor[] propertyArray;
                    Dictionary propertyList = new Dictionary(10); 
                    Type baseType = _type; 
                    Type objType = typeof(object);
 
                    do {
                        propertyArray = ReflectGetProperties(baseType);
                        foreach(PropertyDescriptor p in propertyArray) {
                            if (!propertyList.ContainsKey(p.Name)) { 
                                propertyList.Add(p.Name, p);
                            } 
                        } 
                        baseType = baseType.BaseType;
                    } 
                    while(baseType != null && baseType != objType);

                    propertyArray = new PropertyDescriptor[propertyList.Count];
                    propertyList.Values.CopyTo(propertyArray, 0); 
                    _properties = new PropertyDescriptorCollection(propertyArray, true);
                } 
 
                return _properties;
            } 

            /// 
            ///     Retrieves a type from a name.  The Assembly of the type
            ///     that this PropertyDescriptor came from is first checked, 
            ///     then a global Type.GetType is performed.
            ///  
            private Type GetTypeFromName(string typeName) 
            {
 
                if (typeName == null || typeName.Length == 0)
                {
                     return null;
                } 

                int commaIndex = typeName.IndexOf(','); 
                Type t = null; 

                if (commaIndex == -1) 
                {
                    t = _type.Assembly.GetType(typeName);
                }
 
                if (t == null)
                { 
                    t = Type.GetType(typeName); 
                }
 
                if (t == null && commaIndex != -1)
                {
                    // At design time, it's possible for us to reuse
                    // an assembly but add new types.  The app domain 
                    // will cache the assembly based on identity, however,
                    // so it could be looking in the previous version 
                    // of the assembly and not finding the type.  We work 
                    // around this by looking for the non-assembly qualified
                    // name, which causes the domain to raise a type 
                    // resolve event.
                    //
                    t = Type.GetType(typeName.Substring(0, commaIndex));
                } 

                return t; 
            } 

            ///  
            ///     Refreshes the contents of this type descriptor.  This does not
            ///     actually requery, but it will clear our state so the next
            ///     query re-populates.
            ///  
            internal void Refresh()
            { 
                _attributes = null; 
                _events = null;
                _properties = null; 
                _converter = null;
                _editors = null;
                _editorTypes = null;
                _editorCount = 0; 
            }
        } 
    } 
}
                        

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