Perf: Cache change detector in state manager CascadeDelete (#22261)

Resolves #22215

Author: smitpatel

src/EFCore/ChangeTracking/Internal/StateManager.cs

@@ -44,6 +44,8 @@ private readonly EntityReferenceMap _entityReferenceMap
         private IIdentityMap _identityMap1;
         private Dictionary<IKey, IIdentityMap> _identityMaps;
         private bool _needsUnsubscribe;
+        private IChangeDetector _changeDetector;
+        private bool _changeDetectorInitialized;
 
         private readonly IDiagnosticsLogger<DbLoggerCategory.ChangeTracking> _changeTrackingLogger;
         private readonly IInternalEntityEntryFactory _internalEntityEntryFactory;
@@ -81,6 +83,7 @@ public StateManager([NotNull] StateManagerDependencies dependencies)
 
             UpdateLogger = dependencies.UpdateLogger;
             _changeTrackingLogger = dependencies.ChangeTrackingLogger;
+            _changeDetectorInitialized = false;
         }
 
         /// <summary>
@@ -987,10 +990,14 @@ public virtual void CascadeDelete(InternalEntityEntry entry, bool force, IEnumer
         {
             var doCascadeDelete = force || CascadeDeleteTiming != CascadeTiming.Never;
             var principalIsDetached = entry.EntityState == EntityState.Detached;
-            var changeDetector = Context.ChangeTracker.AutoDetectChangesEnabled
-                && (string)Context.Model[CoreAnnotationNames.SkipDetectChangesAnnotation] != "true"
-                    ? Context.GetDependencies().ChangeDetector
-                    : null;
+            if (!_changeDetectorInitialized)
+            {
+                _changeDetector = Context.ChangeTracker.AutoDetectChangesEnabled
+                    && (string)Context.Model[CoreAnnotationNames.SkipDetectChangesAnnotation] != "true"
+                        ? Context.GetDependencies().ChangeDetector
+                        : null;
+                _changeDetectorInitialized = true;
+            }
 
             foreignKeys ??= entry.EntityType.GetReferencingForeignKeys();
             foreach (var fk in foreignKeys)
@@ -1008,7 +1015,7 @@ public virtual void CascadeDelete(InternalEntityEntry entry, bool force, IEnumer
                         continue;
                     }
 
-                    changeDetector?.DetectChanges(dependent);
+                    _changeDetector?.DetectChanges(dependent);
 
                     if (dependent.EntityState != EntityState.Deleted
                         && dependent.EntityState != EntityState.Detached