fix: Eliminates List allocations in various places.

Projects/Server/Items/Container.cs

@@ -425,8 +425,8 @@ public virtual bool TryDropItem(Mobile from, Item dropped, bool sendFullMessage,
 
     public virtual bool TryDropItems(Mobile from, bool sendFullMessage, params ReadOnlySpan<Item> droppedItems)
     {
-        var dropItems = new List<Item>();
-        var stackItems = new List<ItemStackEntry>();
+        using var dropItems = PooledRefQueue<Item>.Create();
+        using var stackItems = PooledRefQueue<ItemStackEntry>.Create();
 
         var extraItems = 0;
         var extraWeight = 0;
@@ -446,7 +446,7 @@ public virtual bool TryDropItems(Mobile from, bool sendFullMessage, params ReadO
                 if (item is not Container && CheckHold(from, dropped, false, false, 0, extraWeight) &&
                     item.CanStackWith(dropped))
                 {
-                    stackItems.Add(new ItemStackEntry(item, dropped));
+                    stackItems.Enqueue(new ItemStackEntry(item, dropped));
                     extraWeight += (int)Math.Ceiling(item.Weight * (item.Amount + dropped.Amount)) -
                                    item.PileWeight; // extra weight delta, do not need TotalWeight as we do not have hybrid stackable container types
                     stacked = true;
@@ -456,22 +456,23 @@ public virtual bool TryDropItems(Mobile from, bool sendFullMessage, params ReadO
 
             if (!stacked && CheckHold(from, dropped, false, true, extraItems, extraWeight))
             {
-                dropItems.Add(dropped);
+                dropItems.Enqueue(dropped);
                 extraItems++;
                 extraWeight += dropped.TotalWeight + dropped.PileWeight;
             }
         }
 
         if (dropItems.Count + stackItems.Count == droppedItems.Length) // All good
         {
-            for (var i = 0; i < dropItems.Count; i++)
+            while (dropItems.Count > 0)
             {
-                DropItem(dropItems[i]);
+                DropItem(dropItems.Dequeue());
             }
 
-            for (var i = 0; i < stackItems.Count; i++)
+            while (stackItems.Count > 0)
             {
-                stackItems[i].m_StackItem.StackWith(from, stackItems[i].m_DropItem, false);
+                var stackItem = stackItems.Dequeue();
+                stackItem.m_StackItem.StackWith(from, stackItem.m_DropItem, false);
             }
 
             return true;

Projects/Server/Regions/Region.cs

@@ -547,10 +547,29 @@ public Region GetRegion(string regionName, bool caseSensitive = true)
     public virtual bool AcceptsSpawnsFrom(Region region) =>
         AllowSpawn() && (region == this || Parent?.AcceptsSpawnsFrom(region) == true);
 
-    public List<Mobile> GetPlayers()
+    public PooledRefList<Mobile> GetPlayersPooled()
     {
-        var list = new List<Mobile>();
+        var list = PooledRefList<Mobile>.Create();
+        for (var i = 0; i < Sectors?.Length; i++)
+        {
+            var sector = Sectors[i];
+
+            foreach (var ns in sector.Clients)
+            {
+                var player = ns.Mobile;
+                if (player?.Deleted == false && player.Region.IsPartOf(this))
+                {
+                    list.Add(ns.Mobile);
+                }
+            }
+        }
+
+        return list;
+    }
 
+    public List<Mobile> GetPlayers()
+    {
+        List<Mobile> list = [];
         for (var i = 0; i < Sectors?.Length; i++)
         {
             var sector = Sectors[i];
@@ -609,6 +628,25 @@ public List<Mobile> GetMobiles()
         return list;
     }
 
+    public PooledRefList<Mobile> GetMobilesPooled()
+    {
+        var list = PooledRefList<Mobile>.Create();
+        for (var i = 0; i < Sectors?.Length; i++)
+        {
+            var sector = Sectors[i];
+
+            foreach (var mobile in sector.Mobiles)
+            {
+                if (mobile.Region.IsPartOf(this))
+                {
+                    list.Add(mobile);
+                }
+            }
+        }
+
+        return list;
+    }
+
     public int GetMobileCount()
     {
         var count = 0;
@@ -649,6 +687,26 @@ public List<Item> GetItems()
         return list;
     }
 
+    public PooledRefList<Item> GetItemsPooled()
+    {
+        var list = PooledRefList<Item>.Create();
+
+        for (var i = 0; i < Sectors?.Length; i++)
+        {
+            var sector = Sectors[i];
+
+            foreach (var item in sector.Items)
+            {
+                if (Find(item.Location, item.Map).IsPartOf(this))
+                {
+                    list.Add(item);
+                }
+            }
+        }
+
+        return list;
+    }
+
     public int GetItemCount()
     {
         var count = 0;

Projects/UOContent/Accounting/Account.cs

@@ -849,40 +849,6 @@ private bool UpgradePassword(string password, PasswordProtectionAlgorithm algori
         return true;
     }
 
-    /// <summary>
-    ///     Deserializes a list of string values from an xml element. Null values are not added to the list.
-    /// </summary>
-    /// <param name="node">The XmlElement from which to deserialize.</param>
-    /// <returns>String list. Value will never be null.</returns>
-    private static string[] LoadAccessCheck(XmlElement node)
-    {
-        string[] stringList;
-        var accessCheck = node["accessCheck"];
-
-        if (accessCheck != null)
-        {
-            var list = new List<string>();
-
-            foreach (XmlElement ip in accessCheck.GetElementsByTagName("ip"))
-            {
-                var text = Utility.GetText(ip, null);
-
-                if (text != null)
-                {
-                    list.Add(text);
-                }
-            }
-
-            stringList = list.ToArray();
-        }
-        else
-        {
-            stringList = [];
-        }
-
-        return stringList;
-    }
-
     /// <summary>
     ///     Deserializes a list of IPAddress values from an xml element.
     /// </summary>

Projects/UOContent/Commands/Generic/Commands/DesignInsert.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Server.Collections;
 using Server.Gumps;
 using Server.Items;
 using Server.Multis;
@@ -112,7 +113,7 @@ private void OnConfirmCallback(Mobile from, bool okay, List<object> list, bool s
 
             if (okay)
             {
-                var foundations = new List<HouseFoundation>();
+                using var foundations = PooledRefQueue<HouseFoundation>.Create();
                 flushToLog = list.Count > 20;
 
                 for (var i = 0; i < list.Count; ++i)
@@ -127,7 +128,7 @@ private void OnConfirmCallback(Mobile from, bool okay, List<object> list, bool s
 
                                 if (!foundations.Contains(house))
                                 {
-                                    foundations.Add(house);
+                                    foundations.Enqueue(house);
                                 }
 
                                 break;
@@ -146,9 +147,9 @@ private void OnConfirmCallback(Mobile from, bool okay, List<object> list, bool s
                     }
                 }
 
-                foreach (var house in foundations)
+                while (foundations.Count > 0)
                 {
-                    house.Delta(ItemDelta.Update);
+                    foundations.Dequeue().Delta(ItemDelta.Update);
                 }
             }
             else

Projects/UOContent/Commands/Generic/Implementors/RegionCommandImplementor.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Server.Collections;
 
 namespace Server.Commands.Generic
 {
@@ -33,8 +34,10 @@
 
                 if (mobiles)
                 {
-                    foreach (var mob in reg.GetMobiles())
+                    using var mobileList = reg.GetMobilesPooled();
+                    for (var i = 0; i < mobileList.Count; i++)
                     {
+                        var mob = mobileList[i];
                         if (BaseCommand.IsAccessible(from, mob) && ext.IsValid(mob))
                         {
                             list.Add(mob);
@@ -44,7 +47,8 @@
 
                 if (items)
                 {
-                    foreach (var item in reg.GetItems())
+                    using var itemList = reg.GetItemsPooled();
+                    foreach (var item in itemList)
                     {
                         if (BaseCommand.IsAccessible(from, item) && ext.IsValid(item))
                         {

Projects/UOContent/Engines/CannedEvil/CannedEvilTimer.cs

@@ -15,6 +15,7 @@
 
 using System;
 using System.Collections.Generic;
+using Server.Collections;
 using Server.Misc;
 
 namespace Server.Engines.CannedEvil
@@ -38,58 +39,60 @@ public static void Initialize()
         public static void AddSpawn(DungeonChampionSpawn spawn)
         {
             _dungeonSpawns.Add(spawn);
-            Instance?.OnSlice(_dungeonSpawns, false);
+            OnSlice(_dungeonSpawns, false);
         }
 
         public static void AddSpawn(LLChampionSpawn spawn)
         {
             _lostLandsSpawns.Add(spawn);
-            Instance?.OnSlice(_lostLandsSpawns, false);
+            OnSlice(_lostLandsSpawns, false);
         }
 
         public static void RemoveSpawn(DungeonChampionSpawn spawn)
         {
             _dungeonSpawns.Remove(spawn);
-            Instance?.OnSlice(_dungeonSpawns, false);
+            OnSlice(_dungeonSpawns, false);
         }
 
         public static void RemoveSpawn(LLChampionSpawn spawn)
         {
             _lostLandsSpawns.Remove(spawn);
-            Instance?.OnSlice(_lostLandsSpawns, false);
+            OnSlice(_lostLandsSpawns, false);
         }
 
         public CannedEvilTimer() : base(TimeSpan.Zero, TimeSpan.FromMinutes(1.0))
         {
             _sliceTime = Core.Now;
         }
 
-        public void OnSlice<T>(ICollection<T> list, bool rotate = true) where T : ChampionSpawn
+        public static void OnSlice<T>(ICollection<T> list, bool rotate = true) where T : ChampionSpawn
         {
-            if (list.Count > 0)
+            if (list.Count <= 0)
             {
-                List<T> valid = new List<T>();
+                return;
+            }
+
+            using var valid = PooledRefQueue<IEntity>.Create();
 
-                foreach (T spawn in list)
+            foreach (T spawn in list)
+            {
+                if (spawn.AlwaysActive && !spawn.Active)
                 {
-                    if (spawn.AlwaysActive && !spawn.Active)
-                    {
-                        spawn.ReadyToActivate = true;
-                    }
-                    else if (rotate && (!spawn.Active || spawn.Kills == 0 && spawn.Level == 0))
-                    {
-                        spawn.Active = false;
-                        spawn.ReadyToActivate = false;
-
-                        valid.Add(spawn);
-                    }
+                    spawn.ReadyToActivate = true;
                 }
-
-                if (valid.Count > 0)
+                else if (rotate && (!spawn.Active || spawn.Kills == 0 && spawn.Level == 0))
                 {
-                    valid[Utility.Random(valid.Count)].ReadyToActivate = true;
+                    spawn.Active = false;
+                    spawn.ReadyToActivate = false;
+
+                    valid.Enqueue(spawn);
                 }
             }
+
+            if (valid.Count > 0 && valid.PeekRandom() is T t)
+            {
+                t.ReadyToActivate = true;
+            }
         }
 
         protected override void OnTick()

Projects/UOContent/Engines/CannedEvil/ChampionSpawn.cs

@@ -18,6 +18,7 @@
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
 using ModernUO.Serialization;
+using Server.Collections;
 using Server.Engines.Virtues;
 using Server.Gumps;
 using Server.Items;
@@ -1364,15 +1365,15 @@
         global = Math.Max(global, 1 + Spawn.Level);	//This is a guesstimate.  TODO: Verify & get exact values // OSI testing: at 2 red skulls, light = 0x3 ; 1 red = 0x3.; 3 = 8; 9 = 0xD 8 = 0xD 12 = 0x12 10 = 0xD
     }
 
+    private static readonly HashSet<IPAddress> _addresses = [];
+
     public override void OnEnter(Mobile m)
     {
         if (!m.Player || m.AccessLevel != AccessLevel.Player || Spawn.Active)
         {
             return;
         }
 
-        Region parent = Parent ?? this;
-
         if (Spawn.ReadyToActivate)
         {
             Spawn.Start();
@@ -1384,27 +1385,29 @@
             return;
         }
 
-        List<Mobile> players = parent.GetPlayers();
-        List<IPAddress> addresses = new List<IPAddress>();
+        using var players = (Parent ?? this).GetPlayersPooled();
+
         for (var i = 0; i < players.Count; i++)
         {
-            if (players[i].AccessLevel == AccessLevel.Player && players[i].NetState != null &&
-                !addresses.Contains(players[i].NetState.Address) && !((PlayerMobile)players[i]).Young)
+            var player = players[i];
+            if (player.AccessLevel == AccessLevel.Player && player.NetState != null && !((PlayerMobile)player).Young)
             {
-                addresses.Add(players[i].NetState.Address);
+                _addresses.Add(player.NetState.Address);
             }
         }
 
-        if (addresses.Count >= 15)
+        if (_addresses.Count >= 15)
         {
-            foreach (Mobile player in players)
+            for (var i = 0; i < players.Count; i++)
             {
-                player.SendMessage(0x20, Spawn.BroadcastMessage);
+                players[i].SendMessage(0x20, Spawn.BroadcastMessage);
             }
 
             Spawn.ActivatedByProximity = true;
             Spawn.BeginRestart(TimeSpan.FromMinutes(5.0));
         }
+
+        _addresses.Clear();
     }
 
     public override bool OnMoveInto(Mobile m, Direction d, Point3D newLocation, Point3D oldLocation)