A benchmark showing issue #1252

bench/Autofac.Benchmarks/Benchmarks.cs

@@ -28,7 +28,8 @@ public static class Benchmarks
             typeof(PropertyInjectionBenchmark),
             typeof(RootContainerResolveBenchmark),
             typeof(OpenGenericBenchmark),
-            typeof(MultiConstructorBenchmark)
+            typeof(MultiConstructorBenchmark),
+            typeof(OnActivatedBenchmark)
         };
     }
 }

bench/Autofac.Benchmarks/OnActivatedBenchmark.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+using BenchmarkDotNet.Attributes;
+
+namespace Autofac.Benchmarks
+{
+    public class OnActivatedBenchmark
+    {
+        [Benchmark]
+        public void ResolveWithOnActivatedWithAction()
+        {
+            var builder = new ContainerBuilder();
+            Action<ContainerBuilder> someAction;
+            builder
+                .RegisterType<FakeService>()
+                .OnActivated(c =>
+                {
+                    someAction = b =>
+                    {
+                        b.RegisterInstance(c.Instance);
+                    };
+                });
+            using var container = builder.Build();
+            container.Resolve<FakeService>();
+        }
+
+        internal class FakeService
+        {
+            private IEnumerable<int> _data;
+            public FakeService()
+            {
+                _data = new int[1000];
+            }
+        }
+    }
+}