Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/UI/WebParts/WebPartTransformerAttribute.cs

@@ -0,0 +1,102 @@
+//------------------------------------------------------------------------------
+// <copyright file="WebPartTransformerAttribute.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//------------------------------------------------------------------------------
+
+namespace System.Web.UI.WebControls.WebParts {
+
+    using System;
+    using System.Collections;
+    using System.Collections.Generic;
+    using System.ComponentModel;
+    using System.Diagnostics;
+
+    [AttributeUsage(AttributeTargets.Class)]
+    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];
+        }
+
+        /// <devdoc>
+        /// Returns the types a transformer can accept on its "connection points"
+        /// </devdoc>
+        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;
+        }
+    }
+}