WebPartTransformerAttribute.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / UI / WebParts / WebPartTransformerAttribute.cs / 1 / WebPartTransformerAttribute.cs
                        

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

namespace System.Web.UI.WebControls.WebParts { 
 
    using System;
    using System.Collections; 
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Diagnostics;
    using System.Security.Permissions; 

    [AttributeUsage(AttributeTargets.Class)] 
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)] 
    public sealed class WebPartTransformerAttribute : Attribute {
 
        // Cache provider and consumer types for each WebPartTransformer type. We store an array of
        // 2 Types (consumer, provider) indexed by transformer type.
        private static readonly Hashtable transformerCache = Hashtable.Synchronized(new Hashtable());
 
        private Type _consumerType;
        private Type _providerType; 
 
        public WebPartTransformerAttribute(Type consumerType, Type providerType) {
            if (consumerType == null) { 
                throw new ArgumentNullException("consumerType");
            }

            if (providerType == null) { 
                throw new ArgumentNullException("providerType");
            } 
 
            _consumerType = consumerType;
            _providerType = providerType; 
        }

        public Type ConsumerType {
            get { 
                return _consumerType;
            } 
        } 

        public Type ProviderType { 
            get {
                return _providerType;
            }
        } 

        public static Type GetConsumerType(Type transformerType) { 
            return GetTransformerTypes(transformerType)[0]; 
        }
 
        public static Type GetProviderType(Type transformerType) {
            return GetTransformerTypes(transformerType)[1];
        }
 
        /// 
        /// Returns the types a transformer can accept on its "connection points" 
        ///  
        private static Type[] GetTransformerTypes(Type transformerType) {
            if (transformerType == null) { 
                throw new ArgumentNullException("transformerType");
            }

            if (!transformerType.IsSubclassOf(typeof(WebPartTransformer))) { 
                throw new InvalidOperationException(
                    SR.GetString(SR.WebPartTransformerAttribute_NotTransformer, transformerType.FullName)); 
            } 

            Type[] types = (Type[])transformerCache[transformerType]; 
            if (types == null) {
                types = GetTransformerTypesFromAttribute(transformerType);
                transformerCache[transformerType] = types;
            } 

            return types; 
        } 

        private static Type[] GetTransformerTypesFromAttribute(Type transformerType) { 
            Type[] types = new Type[2];

            object[] attributes = transformerType.GetCustomAttributes(typeof(WebPartTransformerAttribute), true);
            // WebPartTransformerAttribute.AllowMultiple is false 
            Debug.Assert(attributes.Length == 0 || attributes.Length == 1);
            if (attributes.Length == 1) { 
                WebPartTransformerAttribute attribute = (WebPartTransformerAttribute)attributes[0]; 
                if (attribute.ConsumerType == attribute.ProviderType) {
                    throw new InvalidOperationException(SR.GetString(SR.WebPartTransformerAttribute_SameTypes)); 
                }
                types[0] = attribute.ConsumerType;
                types[1] = attribute.ProviderType;
            } 
            else {
                throw new InvalidOperationException( 
                    SR.GetString(SR.WebPartTransformerAttribute_Missing, transformerType.FullName)); 
            }
 
            return types;
        }
    }
}

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