Restore original value when setting IsModified false on navigation

src/EFCore/ChangeTracking/NavigationEntry.cs

@@ -260,7 +260,7 @@ private void SetFkPropertiesModified(InternalEntityEntry internalEntityEntry, bo
                 if (anyNonPk
                     && !property.IsPrimaryKey())
                 {
-                    internalEntityEntry.SetPropertyModified(property, isModified: modified, acceptChanges: true);
+                    internalEntityEntry.SetPropertyModified(property, isModified: modified, acceptChanges: false);
                 }
             }
         }

test/EFCore.Tests/ChangeTracking/CollectionEntryTest.cs

@@ -429,11 +429,14 @@ public void IsModified_can_set_fk_to_modified_principal_with_Modified_dependents
             EntityState principalState, EntityState dependentState)
         {
             using var context = new FreezerContext();
-            var cherry = new Cherry();
+            var cherry = new Cherry { Id = 1 };
             var chunky1 = new Chunky { Id = 1, Garcia = cherry };
             var chunky2 = new Chunky { Id = 2, Garcia = cherry };
             cherry.Monkeys = new List<Chunky> { chunky1, chunky2 };
 
+            context.Attach(chunky1);
+            context.Attach(chunky2);
+
             context.Entry(cherry).State = principalState;
             context.Entry(chunky1).State = dependentState;
             context.Entry(chunky2).State = dependentState;

test/EFCore.Tests/ChangeTracking/ReferenceEntryTest.cs

@@ -351,6 +351,37 @@ public void IsModified_can_set_fk_to_modified()
             Assert.Equal(EntityState.Unchanged, entityEntry.State);
         }
 
+        [ConditionalFact]
+        public void IsModified_can_reject_changes_to_an_fk()
+        {
+            using var context = new FreezerContext();
+            var cherry = new Cherry();
+            var chunky = new Chunky { Garcia = cherry };
+            cherry.Monkeys = new List<Chunky> { chunky };
+            context.AttachRange(cherry, chunky);
+
+            var entityEntry = context.Entry(chunky);
+            var reference = entityEntry.Reference(e => e.Garcia);
+            var originalValue = entityEntry.Property(e => e.GarciaId).CurrentValue;
+
+            Assert.False(reference.IsModified);
+
+            entityEntry.Property(e => e.GarciaId).CurrentValue = 77;
+
+            Assert.True(reference.IsModified);
+            Assert.True(entityEntry.Property(e => e.GarciaId).IsModified);
+            Assert.Equal(77, entityEntry.Property(e => e.GarciaId).CurrentValue);
+            Assert.Equal(originalValue, entityEntry.Property(e => e.GarciaId).OriginalValue);
+
+            reference.IsModified = false;
+
+            Assert.False(reference.IsModified);
+            Assert.False(entityEntry.Property(e => e.GarciaId).IsModified);
+            Assert.Equal(originalValue, entityEntry.Property(e => e.GarciaId).CurrentValue);
+            Assert.Equal(originalValue, entityEntry.Property(e => e.GarciaId).OriginalValue);
+            Assert.Equal(EntityState.Unchanged, entityEntry.State);
+        }
+
         [ConditionalFact]
         public void IsModified_tracks_state_of_FK_property_principal()
         {
@@ -454,10 +485,12 @@ public void IsModified_can_set_fk_to_modified_principal_with_Modified_dependent(
             EntityState principalState, EntityState dependentState)
         {
             using var context = new FreezerContext();
-            var half = new Half();
+            var half = new Half { Id = 7 };
             var chunky = new Chunky { Id = 1, Baked = half };
             half.Monkey = chunky;
 
+            context.Attach(half);
+
             context.Entry(chunky).State = principalState;
             context.Entry(half).State = dependentState;