From bbef15a09bbfce2da98c6e20ca6d04108b3fa89e Mon Sep 17 00:00:00 2001
From: ajcvickers <ajcvickers@hotmail.com>
Date: Mon, 7 Sep 2020 14:58:12 -0700
Subject: [PATCH] Stop attempting to do local DetectChanges when not snapshot
 change-tracking

Fixes #21835
---
 .../ChangeTracking/Internal/ChangeDetector.cs |  8 ++++++--
 .../Internal/ChangeDetectorTest.cs            | 19 +++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/EFCore/ChangeTracking/Internal/ChangeDetector.cs b/src/EFCore/ChangeTracking/Internal/ChangeDetector.cs
index 0f5c632c78c..884dcf902b1 100644
--- a/src/EFCore/ChangeTracking/Internal/ChangeDetector.cs
+++ b/src/EFCore/ChangeTracking/Internal/ChangeDetector.cs
@@ -156,8 +156,7 @@ public virtual void DetectChanges(IStateManager stateManager)
 
             foreach (var entry in stateManager.ToList()) // Might be too big, but usually _all_ entities are using Snapshot tracking
             {
-                if (entry.EntityType.GetChangeTrackingStrategy() == ChangeTrackingStrategy.Snapshot
-                    && entry.EntityState != EntityState.Detached)
+                if (entry.EntityState != EntityState.Detached)
                 {
                     LocalDetectChanges(entry);
                 }
@@ -199,6 +198,11 @@ private void LocalDetectChanges(InternalEntityEntry entry)
         {
             var entityType = entry.EntityType;
 
+            if (entry.EntityType.GetChangeTrackingStrategy() != ChangeTrackingStrategy.Snapshot)
+            {
+                return;
+            }
+
             foreach (var property in entityType.GetProperties())
             {
                 if (property.GetOriginalValueIndex() >= 0
diff --git a/test/EFCore.Tests/ChangeTracking/Internal/ChangeDetectorTest.cs b/test/EFCore.Tests/ChangeTracking/Internal/ChangeDetectorTest.cs
index 37c7e332a0b..b59cab95f74 100644
--- a/test/EFCore.Tests/ChangeTracking/Internal/ChangeDetectorTest.cs
+++ b/test/EFCore.Tests/ChangeTracking/Internal/ChangeDetectorTest.cs
@@ -390,6 +390,25 @@ public void Skips_detection_of_scalar_property_change_for_notification_entities(
             Assert.False(entry.IsModified(entry.EntityType.FindProperty("Name")));
         }
 
+        [ConditionalFact]
+        public void Skips_local_detection_of_scalar_property_change_for_notification_entities()
+        {
+            var contextServices = InMemoryTestHelpers.Instance.CreateContextServices(BuildModelWithChanged());
+
+            var changeDetector = contextServices.GetRequiredService<IChangeDetector>();
+
+            var category = new CategoryWithChanged { Id = 1, Name = "Oculus Rift" };
+            var entry = contextServices.GetRequiredService<IStateManager>().GetOrCreateEntry(category);
+            entry.SetEntityState(EntityState.Unchanged);
+
+            category.Name = "Gear VR";
+
+            changeDetector.DetectChanges(entry);
+
+            Assert.Equal(EntityState.Unchanged, entry.EntityState);
+            Assert.False(entry.IsModified(entry.EntityType.FindProperty("Name")));
+        }
+
         [ConditionalFact]
         public void Detects_principal_key_change()
         {