From 15e6f8fa0edeac001a64148932e49283b1820eb5 Mon Sep 17 00:00:00 2001
From: Stephen Toub <stoub@microsoft.com>
Date: Sun, 18 Apr 2021 14:53:39 -0400
Subject: [PATCH 1/2] Add metadata update handler to
 System.ComponentModel.TypeConverter

---
 ...System.ComponentModel.TypeConverter.csproj |  2 +
 .../ReflectTypeDescriptionProvider.cs         |  9 +++++
 .../ReflectionCachesUpdateHandler.cs          | 39 +++++++++++++++++++
 .../ReflectionCachesUpdateHandlerTests.cs     | 32 +++++++++++++++
 ....ComponentModel.TypeConverter.Tests.csproj |  1 +
 5 files changed, 83 insertions(+)
 create mode 100644 src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectionCachesUpdateHandler.cs
 create mode 100644 src/libraries/System.ComponentModel.TypeConverter/tests/ReflectionCachesUpdateHandlerTests.cs

diff --git a/src/libraries/System.ComponentModel.TypeConverter/src/System.ComponentModel.TypeConverter.csproj b/src/libraries/System.ComponentModel.TypeConverter/src/System.ComponentModel.TypeConverter.csproj
index a93c8e4aadc9d..5312108604e3c 100644
--- a/src/libraries/System.ComponentModel.TypeConverter/src/System.ComponentModel.TypeConverter.csproj
+++ b/src/libraries/System.ComponentModel.TypeConverter/src/System.ComponentModel.TypeConverter.csproj
@@ -70,6 +70,7 @@
     <Compile Include="System\ComponentModel\MemberDescriptor.cs" />
     <Compile Include="System\ComponentModel\PropertyDescriptorCollection.cs" />
     <Compile Include="System\ComponentModel\ProvidePropertyAttribute.cs" />
+    <Compile Include="System\ComponentModel\ReflectionCachesUpdateHandler.cs" />
     <Compile Include="System\ComponentModel\ReflectEventDescriptor.cs" />
     <Compile Include="System\ComponentModel\ReflectPropertyDescriptor.cs" />
     <Compile Include="System\ComponentModel\ReflectTypeDescriptionProvider.cs" />
@@ -253,6 +254,7 @@
     <Reference Include="System.Runtime" />
     <Reference Include="System.Runtime.Extensions" />
     <Reference Include="System.Runtime.InteropServices" />
+    <Reference Include="System.Runtime.Loader" />
     <Reference Include="System.Runtime.Serialization.Formatters" />
     <Reference Include="System.Text.RegularExpressions" />
     <Reference Include="System.Threading" />
diff --git a/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs b/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs
index de3b12258cca6..8962f6c7b5d13 100644
--- a/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs
+++ b/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs
@@ -204,6 +204,15 @@ private static EnumConverter CreateEnumConverter(Type type)
 
         private static Hashtable ExtendedPropertyCache => LazyInitializer.EnsureInitialized(ref s_extendedPropertyCache, () => new Hashtable());
 
+        /// <summary>Clear the global caches this maintains on top of reflection.</summary>
+        internal static void ClearReflectionCaches()
+        {
+            Volatile.Write(ref s_propertyCache, null);
+            Volatile.Write(ref s_eventCache, null);
+            Volatile.Write(ref s_attributeCache, null);
+            Volatile.Write(ref s_extendedPropertyCache, null);
+        }
+
         /// <summary>
         /// Adds an editor table for the given editor base type.
         /// Typically, editors are specified as metadata on an object. If no metadata for a
diff --git a/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectionCachesUpdateHandler.cs b/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectionCachesUpdateHandler.cs
new file mode 100644
index 0000000000000..fe2a5306553a9
--- /dev/null
+++ b/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectionCachesUpdateHandler.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#nullable enable
+using System.ComponentModel;
+using System.Reflection;
+using System.Reflection.Metadata;
+
+[assembly: MetadataUpdateHandler(typeof(ReflectionCachesUpdateHandler))]
+
+namespace System.ComponentModel
+{
+    internal static class ReflectionCachesUpdateHandler
+    {
+        public static void BeforeUpdate(Type[]? types)
+        {
+            // ReflectTypeDescriptionProvider maintains global caches on top of reflection.
+            // Clear those.
+            ReflectTypeDescriptionProvider.ClearReflectionCaches();
+
+            // Each type descriptor may also cache reflection-based state that it gathered
+            // from ReflectTypeDescriptionProvider.  Clear those as well.
+            if (types is not null)
+            {
+                foreach (Type type in types)
+                {
+                    TypeDescriptor.Refresh(type);
+                }
+            }
+            else
+            {
+                foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies())
+                {
+                    TypeDescriptor.Refresh(assembly);
+                }
+            }
+        }
+    }
+}
diff --git a/src/libraries/System.ComponentModel.TypeConverter/tests/ReflectionCachesUpdateHandlerTests.cs b/src/libraries/System.ComponentModel.TypeConverter/tests/ReflectionCachesUpdateHandlerTests.cs
new file mode 100644
index 0000000000000..829bbd5b1edce
--- /dev/null
+++ b/src/libraries/System.ComponentModel.TypeConverter/tests/ReflectionCachesUpdateHandlerTests.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Reflection;
+using Xunit;
+
+namespace System.ComponentModel.Tests
+{
+    [SimpleUpdateTest]
+    public class ReflectionCachesUpdateHandlerTests
+    {
+        [Fact]
+        public void ReflectionCachesUpdateHandler_CachesCleared()
+        {
+            AttributeCollection ac1 = TypeDescriptor.GetAttributes(typeof(ReflectionCachesUpdateHandlerTests));
+            AttributeCollection ac2 = TypeDescriptor.GetAttributes(typeof(ReflectionCachesUpdateHandlerTests));
+            Assert.Equal(ac1.Count, ac2.Count);
+            Assert.Equal(1, ac1.Count);
+            Assert.Same(ac1[0], ac2[0]);
+
+            MethodInfo beforeUpdate = typeof(TypeDescriptionProvider).Assembly.GetType("System.ComponentModel.ReflectionCachesUpdateHandler", throwOnError: true).GetMethod("BeforeUpdate");
+            Assert.NotNull(beforeUpdate);
+            beforeUpdate.Invoke(null, new object[] { null });
+
+            AttributeCollection ac3 = TypeDescriptor.GetAttributes(typeof(ReflectionCachesUpdateHandlerTests));
+            Assert.NotSame(ac1[0], ac3[0]);
+        }
+    }
+
+    [AttributeUsage(AttributeTargets.All)]
+    internal sealed class SimpleUpdateTestAttribute : Attribute { }
+}
diff --git a/src/libraries/System.ComponentModel.TypeConverter/tests/System.ComponentModel.TypeConverter.Tests.csproj b/src/libraries/System.ComponentModel.TypeConverter/tests/System.ComponentModel.TypeConverter.Tests.csproj
index b8a634b041a8f..4f96c81aea140 100644
--- a/src/libraries/System.ComponentModel.TypeConverter/tests/System.ComponentModel.TypeConverter.Tests.csproj
+++ b/src/libraries/System.ComponentModel.TypeConverter/tests/System.ComponentModel.TypeConverter.Tests.csproj
@@ -104,6 +104,7 @@
     <Compile Include="Mocks\MockServiceProvider.cs" />
     <Compile Include="MultilineStringConverterTests.cs" />
     <Compile Include="NullableConverterTests.cs" />
+    <Compile Include="ReflectionCachesUpdateHandlerTests.cs" />
     <Compile Include="PropertyDescriptorCollectionTests.cs" />
     <Compile Include="PropertyDescriptorTests.cs" />
     <Compile Include="ProvidePropertyAttributeTests.cs" />

From 6cab30cb1314e8dd32b48436659534fbd1e0d380 Mon Sep 17 00:00:00 2001
From: Stephen Toub <stoub@microsoft.com>
Date: Mon, 19 Apr 2021 21:04:30 -0400
Subject: [PATCH 2/2] Update
 src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs

---
 .../ComponentModel/ReflectTypeDescriptionProvider.cs      | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs b/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs
index 8962f6c7b5d13..24361c55c829e 100644
--- a/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs
+++ b/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs
@@ -207,10 +207,10 @@ private static EnumConverter CreateEnumConverter(Type type)
         /// <summary>Clear the global caches this maintains on top of reflection.</summary>
         internal static void ClearReflectionCaches()
         {
-            Volatile.Write(ref s_propertyCache, null);
-            Volatile.Write(ref s_eventCache, null);
-            Volatile.Write(ref s_attributeCache, null);
-            Volatile.Write(ref s_extendedPropertyCache, null);
+            s_propertyCache = null;
+            s_eventCache = null;
+            s_attributeCache = null;
+            s_extendedPropertyCache = null;
         }
 
         /// <summary>