From 679b0e0bd923490452e75c98bf466629b87ba175 Mon Sep 17 00:00:00 2001
From: Ziya Suzen <ziya@suzen.net>
Date: Mon, 16 Jun 2025 14:06:46 +0100
Subject: [PATCH] Fix inbox collection was modified exception

---
 src/NATS.Client.Core/Internal/InboxSub.cs | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/NATS.Client.Core/Internal/InboxSub.cs b/src/NATS.Client.Core/Internal/InboxSub.cs
index 1f3402469..f2f1b3cfb 100644
--- a/src/NATS.Client.Core/Internal/InboxSub.cs
+++ b/src/NATS.Client.Core/Internal/InboxSub.cs
@@ -128,13 +128,24 @@ public async ValueTask ReceivedAsync(string subject, string? replyTo, ReadOnlySe
         }
 
 #if NETSTANDARD2_0
-        foreach (var weakReference in subTable)
+        WeakReference<NatsSubBase>[] weakReferences;
+        int subscriptionCount;
+        lock (subTable)
         {
-            if (weakReference.TryGetTarget(out var sub))
+            subscriptionCount = subTable.Count;
+            weakReferences = ArrayPool<WeakReference<NatsSubBase>>.Shared.Rent(subscriptionCount);
+            subTable.CopyTo(weakReferences, 0);
+        }
+
+        for (var i = 0; i < subscriptionCount; i++)
+        {
+            if (weakReferences[i].TryGetTarget(out var sub))
             {
                 await sub.ReceiveAsync(subject, replyTo, headersBuffer, payloadBuffer).ConfigureAwait(false);
             }
         }
+
+        ArrayPool<WeakReference<NatsSubBase>>.Shared.Return(weakReferences);
 #else
         foreach (var (sub, _) in subTable)
         {