src/NLog/Internal/PropertiesDictionary.cs (2)

109-116: Lazy init + insert-aware capacity look solid; minor naming nit

The new GetEventProperties(bool prepareForInsert = false) plus InitalizeEventPropertiesDictionary(...) wiring looks correct:

• Interlocked.CompareExchange ensures _eventProperties is only initialized once, and discarded dictionaries from racing threads can’t overwrite an already-populated instance.
• prepareForInsert is only used at real insert sites (this[key] setter and Add), so the Count + 2 capacity hint is applied exactly when extra headroom is needed.
• Read-only paths (TryGetValue via TryLookupMessagePropertyValue when Count > 10) route through GetEventProperties() without the insert hint, which keeps capacity tight for lookups.

Only nit: the helper name is misspelled (InitalizeEventPropertiesDictionary), which makes it harder to search for and slightly hurts readability. Consider renaming while this code is fresh:

-        private static Dictionary<object, PropertyValue> InitalizeEventPropertiesDictionary(IList<MessageTemplateParameter>? messageProperties, bool prepareForInsert)
+        private static Dictionary<object, PropertyValue> InitializeEventPropertiesDictionary(IList<MessageTemplateParameter>? messageProperties, bool prepareForInsert)
@@
-                System.Threading.Interlocked.CompareExchange(ref _eventProperties, InitalizeEventPropertiesDictionary(_messageProperties, prepareForInsert), null);
+                System.Threading.Interlocked.CompareExchange(ref _eventProperties, InitializeEventPropertiesDictionary(_messageProperties, prepareForInsert), null);

Also applies to: 167-180, 194-217, 324-325, 345-349

---

235-247: Contains/Remove/ValueCollection usage of GetEventProperties preserves semantics; possible micro-optimization

The updated Contains(KeyValuePair<...>), Remove overloads, and ValueCollection.Contains all correctly route through GetEventProperties, keeping message-template and event properties unified in the backing dictionary while respecting IsMessageProperty flags. The guards using IsEmpty and (_eventProperties != null || ContainsKey(...)) avoid unnecessary work when there are truly no properties.

If you ever want to shave a few allocations, a small optional optimization would be:

• In places like ValueCollection.Contains, when _eventProperties is still null and _messageProperties is small (e.g., Count <= 10), you could scan _messageProperties directly instead of materializing the dictionary via GetEventProperties(). That would avoid creating the dictionary for rare Contains calls in tiny message-only cases.

Not required for correctness; current behavior is consistent and clear.

Also applies to: 289-312, 604-616

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

src/NLog/Internal/PropertiesDictionary.cs (1)

167-180: Consider documenting the capacity buffer.

The +2 buffer when prepareForInsert is true reduces rehashing on subsequent inserts. However, this magic number lacks explanation.

Consider adding a comment or named constant to clarify the rationale:

 private static Dictionary<object, PropertyValue> InitializeEventPropertiesDictionary(IList<MessageTemplateParameter>? messageProperties, bool prepareForInsert)
 {
     if (messageProperties?.Count > 0)
     {
-        var dictionaryCapacity = prepareForInsert ? (messageProperties.Count + 2) : messageProperties.Count;
+        // Reserve extra capacity to reduce rehashing when adding event properties alongside message properties
+        const int ExtraCapacityForInserts = 2;
+        var dictionaryCapacity = prepareForInsert ? (messageProperties.Count + ExtraCapacityForInserts) : messageProperties.Count;
         var eventProperties = new Dictionary<object, PropertyValue>(dictionaryCapacity, PropertyKeyComparer.Default);

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro