Fix Equals and GetHashCode override check for proxy generation hooks having multiple Equals methods

CHANGELOG.md

@@ -14,6 +14,7 @@ Bugfixes:
 - `InvalidProgramException` when proxying `MemoryStream` with .NET 7 (@stakx, #651)
 - `invocation.MethodInvocationTarget` throws `ArgumentNullException` for default interface method (@stakx, #684)
 - `DynamicProxyException` ("duplicate element") when type to proxy contains members whose names differ only in case (@stakx, #691)
+- `AmbiguousMatchException` when using a proxy generation hook that is implemented as a `record class` (@stakx, #720)
 
 ## 5.2.1 (2025-03-09)
 

src/Castle.Core.Tests/DynamicProxy.Tests/ProxyTypeCachingWithDifferentHooksTestCase.cs

@@ -15,6 +15,7 @@
 namespace Castle.DynamicProxy.Tests
 {
 	using System;
+	using System.Reflection;
 
 	using Castle.DynamicProxy.Tests.Interceptors;
 	using Castle.DynamicProxy.Tests.Interfaces;
@@ -29,6 +30,47 @@ public class ProxyTypeCachingWithDifferentHooksTestCase : BasePEVerifyTestCase
 #endif
 		public class CustomHook : AllMethodsHook { }
 
+#if FEATURE_SERIALIZATION
+		[Serializable]
+#endif
+		public class EquatableHook : IProxyGenerationHook, IEquatable<EquatableHook>
+		{
+			public override bool Equals(object obj) => Equals(obj as EquatableHook);
+			public override int GetHashCode() => GetType().GetHashCode();
+
+			public bool Equals(EquatableHook other) => other is EquatableHook;
+
+			public void MethodsInspected() { }
+			public void NonProxyableMemberNotification(Type type, MemberInfo memberInfo) { }
+			public bool ShouldInterceptMethod(Type type, MethodInfo methodInfo) => false;
+		}
+
+#if FEATURE_SERIALIZATION
+		[Serializable]
+#endif
+		public record class RecordClassHook : IProxyGenerationHook
+		{
+			public RecordClassHook(string id)
+			{
+				Id = id;
+			}
+
+			public string Id { get; }
+
+			public void MethodsInspected() { }
+			public void NonProxyableMemberNotification(Type type, MemberInfo memberInfo) { }
+			public bool ShouldInterceptMethod(Type type, MethodInfo methodInfo) => false;
+		}
+
+		// `IEquatable<>` can lead to there being more than one `Equals` method.
+		// This is relevant for hook classes because DynamicProxy checks whether they
+		// override the inherited `Equals` method for proper equality semantics.
+		[Test]
+		public void Can_use_hook_that_implements_IEquatable()
+		{
+			_ = CreateProxyWithHook<EquatableHook>();
+		}
+
 		[Test]
 		public void Proxies_with_same_hook_will_use_cached_proxy_type()
 		{
@@ -45,9 +87,42 @@ public void Proxies_with_different_hooks_will_use_different_proxy_types()
 			Assert.AreNotEqual(first.GetType(), second.GetType());
 		}
 
+		[Test]
+		public void Proxies_with_different_but_equal_record_class_hooks_will_use_cached_proxy_type()
+		{
+			var firstHook = new RecordClassHook("1");
+			var secondHook = new RecordClassHook("1");
+			Assume.That(firstHook, Is.Not.SameAs(secondHook));
+			Assume.That(firstHook, Is.EqualTo(secondHook));
+
+			var first = CreateProxyWithHook(firstHook);
+			var second = CreateProxyWithHook(secondHook);
+
+			Assert.AreEqual(first.GetType(), second.GetType());
+		}
+
+		[Test]
+		public void Proxies_with_different_and_unequal_record_class_hooks_will_use_different_proxy_types()
+		{
+			var firstHook = new RecordClassHook("1");
+			var secondHook = new RecordClassHook("2");
+			Assume.That(firstHook, Is.Not.SameAs(secondHook));
+			Assume.That(firstHook, Is.Not.EqualTo(secondHook));
+
+			var first = CreateProxyWithHook(firstHook);
+			var second = CreateProxyWithHook(secondHook);
+
+			Assert.AreNotEqual(first.GetType(), second.GetType());
+		}
+
 		private object CreateProxyWithHook<THook>() where THook : IProxyGenerationHook, new()
 		{
-			return generator.CreateInterfaceProxyWithoutTarget(typeof(IEmpty), new ProxyGenerationOptions(new THook()), new DoNothingInterceptor());
+			return CreateProxyWithHook(new THook());
+		}
+
+		private object CreateProxyWithHook(IProxyGenerationHook hook)
+		{
+			return generator.CreateInterfaceProxyWithoutTarget(typeof(IEmpty), new ProxyGenerationOptions(hook), new DoNothingInterceptor());
 		}
 	}
 }

src/Castle.Core/DynamicProxy/Generators/BaseProxyGenerator.cs

@@ -393,7 +393,7 @@ protected void InitializeStaticFields(Type builtType)
 
 		private bool OverridesEqualsAndGetHashCode(Type type)
 		{
-			var equalsMethod = type.GetMethod("Equals", BindingFlags.Public | BindingFlags.Instance);
+			var equalsMethod = type.GetMethod("Equals", BindingFlags.Public | BindingFlags.Instance, null, [ typeof(object) ], null);
 			if (equalsMethod == null || equalsMethod.DeclaringType == typeof(object) || equalsMethod.IsAbstract)
 			{
 				return false;