Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / CompMod / System / ComponentModel / DelegatingTypeDescriptionProvider.cs / 1 / DelegatingTypeDescriptionProvider.cs
//------------------------------------------------------------------------------ //// Copyright (c) Microsoft Corporation. All rights reserved. // //----------------------------------------------------------------------------- namespace System.ComponentModel { using System; using System.Collections; using System.Reflection; using System.Security.Permissions; ////// This is a simple type description provider that, when invoked demand /// locates the correct type description provider for the given type and /// invokes it. This is used as the tail node for both type and instance /// based providers. Conceptually it "links" the provider list for one type /// or instance to its corresponding base type. /// [HostProtection(SharedState = true)] internal sealed class DelegatingTypeDescriptionProvider : TypeDescriptionProvider { private Type _type; ////// Creates a new DelegatingTypeDescriptionProvider. The type is the /// type we will delegate to. /// internal DelegatingTypeDescriptionProvider(Type type) { _type = type; } ////// /// private TypeDescriptionProvider Provider { get { return TypeDescriptor.GetProviderRecursive(_type); } } ////// This method is used to create an instance that can substitute for another /// data type. If the method is not interested in providing a substitute /// instance, it should call base. /// public override object CreateInstance(IServiceProvider provider, Type objectType, Type[] argTypes, object[] args) { return Provider.CreateInstance(provider, objectType, argTypes, args); } ////// TypeDescriptor may need to perform complex operations on collections of metadata. /// Since types are not unloaded for the life of a domain, TypeDescriptor will /// automatically cache the results of these operations based on type. There are a /// number of operations that use live object instances, however. These operations /// cannot be cached within TypeDescriptor because caching them would prevent the /// object from garbage collecting. Instead, TypeDescriptor allows for a per-object /// cache, accessed as an IDictionary of key/value pairs, to exist on an object. /// The GetCache method returns an instance of this cache. GetCache will return /// null if there is no supported cache for an object. /// public override IDictionary GetCache(object instance) { return Provider.GetCache(instance); } ////// 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 /// GetTypeDescriptor.GetComponentName. /// public override string GetFullComponentName(object component) { return Provider.GetFullComponentName(component); } ////// This method returns an extended custom type descriptor for the given object. /// An extended type descriptor is a custom type descriptor that offers properties /// that other objects have added to this object, but are not actually defined on /// the object. For example, in the .NET Framework Component Model, objects that /// implement the interface IExtenderProvider can "attach" properties to other /// objects that reside in the same logical container. The GetTypeDescriptor /// method does not return a type descriptor that provides these extra extended /// properties. GetExtendedTypeDescriptor returns the set of these extended /// properties. TypeDescriptor will automatically merge the results of these /// two property collections. Note that while the .NET Framework component /// model only supports extended properties this API can be used for extended /// attributes and events as well, if the type description provider supports it. /// public override ICustomTypeDescriptor GetExtendedTypeDescriptor(object instance) { return Provider.GetExtendedTypeDescriptor(instance); } ////// The GetReflection method is a lower level version of GetTypeDescriptor. /// If no custom type descriptor can be located for an object, GetReflection /// is called to perform normal reflection against the object. /// public override Type GetReflectionType(Type objectType, object instance) { return Provider.GetReflectionType(objectType, instance); } ////// 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) { return Provider.GetTypeDescriptor(objectType, instance); } } }
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