Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web.Extensions/ui/AssemblyCache.cs

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+//------------------------------------------------------------------------------
+// <copyright file="AssemblyCache.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//------------------------------------------------------------------------------
+
+namespace System.Web.UI {
+    using System;
+using System.Collections;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
+using System.Web.Configuration;
+using System.Web.Script;
+
+    // Caches Assembly APIs to improve performance
+    internal static class AssemblyCache {
+        // PERF: Cache reference to System.Web.Extensions assembly. Use ScriptManager since it's guaranteed to be in S.W.E
+        public static readonly Assembly SystemWebExtensions = typeof(ScriptManager).Assembly;
+        public static readonly Assembly SystemWeb = typeof(Page).Assembly;
+
+        private static CompilationSection _compilationSection;
+        internal static bool _useCompilationSection = true;
+
+        // Maps string (assembly name) to Assembly
+        private static readonly Hashtable _assemblyCache = Hashtable.Synchronized(new Hashtable());
+        // Maps assembly to Version
+        // internal so it can be manipulated by the unit test suite
+        internal static readonly Hashtable _versionCache = Hashtable.Synchronized(new Hashtable());
+        // Maps an assembly to its ajax framework assembly attribute. If it doesn't have one, it maps it to a null value
+        private static readonly ConcurrentDictionary<Assembly, AjaxFrameworkAssemblyAttribute> _ajaxAssemblyAttributeCache =
+            new ConcurrentDictionary<Assembly, AjaxFrameworkAssemblyAttribute>();
+
+        private static CompilationSection CompilationSection {
+            get {
+                if (_compilationSection == null) {
+                    _compilationSection = RuntimeConfig.GetAppConfig().Compilation;
+                }
+                return _compilationSection;
+            }
+        }
+
+        public static Version GetVersion(Assembly assembly) {
+            Debug.Assert(assembly != null);
+            Version version = (Version)_versionCache[assembly];
+            if (version == null) {
+                // use new AssemblyName() instead of assembly.GetName() so it works in medium trust
+                version = new AssemblyName(assembly.FullName).Version;
+                _versionCache[assembly] = version;
+            }
+            return version;
+        }
+
+        public static Assembly Load(string assemblyName) {
+            Debug.Assert(!String.IsNullOrEmpty(assemblyName));
+            Assembly assembly = (Assembly)_assemblyCache[assemblyName];
+            if (assembly == null) {
+                // _useCompilationSection must be set to false in a unit test environment since there
+                // is no http runtime, and therefore no trust level is set.
+                if (_useCompilationSection) {
+                    assembly = CompilationSection.LoadAssembly(assemblyName, true);
+                }
+                else {
+                    assembly = Assembly.Load(assemblyName);
+                }
+                _assemblyCache[assemblyName] = assembly;
+            }
+            return assembly;
+        }
+
+        public static bool IsAjaxFrameworkAssembly(Assembly assembly) {
+            return (GetAjaxFrameworkAssemblyAttribute(assembly) != null);
+        }
+
+        public static AjaxFrameworkAssemblyAttribute GetAjaxFrameworkAssemblyAttribute(Assembly assembly) {
+            Debug.Assert(assembly != null);
+            AjaxFrameworkAssemblyAttribute ajaxFrameworkAssemblyAttribute;
+            if (!_ajaxAssemblyAttributeCache.TryGetValue(assembly, out ajaxFrameworkAssemblyAttribute)) {
+                 ajaxFrameworkAssemblyAttribute = SafeGetAjaxFrameworkAssemblyAttribute(assembly);
+                _ajaxAssemblyAttributeCache.TryAdd(assembly, ajaxFrameworkAssemblyAttribute);
+            }
+            return ajaxFrameworkAssemblyAttribute;
+        }
+
+        [SuppressMessage("Microsoft.Design", "CA1031:DoNotCatchGeneralExceptionTypes", Justification = "We do not want to throw from this method.")]
+        internal static AjaxFrameworkAssemblyAttribute SafeGetAjaxFrameworkAssemblyAttribute(ICustomAttributeProvider attributeProvider) {
+            try {
+                foreach (Attribute attribute in attributeProvider.GetCustomAttributes(inherit: false)) {
+                    AjaxFrameworkAssemblyAttribute ajaxFrameworkAttribute = attribute as AjaxFrameworkAssemblyAttribute;
+                    if (ajaxFrameworkAttribute != null) {
+                        return ajaxFrameworkAttribute;
+                    }
+                }
+            }
+            catch {
+                // Bug 34311: If we are unable to load the attribute, don't throw. 
+            }
+            return null;
+        }
+    }
+}