DelegatingTypeDescriptionProvider.cs source code in C# .NET

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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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