diff --git a/OpenSim/Framework/AgentCircuitData.cs b/OpenSim/Framework/AgentCircuitData.cs
index 5c64839a3f..7242993a45 100644
--- a/OpenSim/Framework/AgentCircuitData.cs
+++ b/OpenSim/Framework/AgentCircuitData.cs
@@ -97,7 +97,7 @@ namespace OpenSim.Framework
         /// <summary>
         /// Agent's full name.
         /// </summary>
-        public string Name { get { return string.Format("{0} {1}", firstname, lastname); } }
+        public string Name { get { return $"{firstname} {lastname}"; } }
 
         /// <summary>
         /// Random Unique GUID for this session.  Client gets this at login and it's
@@ -139,13 +139,13 @@ namespace OpenSim.Framework
             get
             {
                 // Old style version string contains viewer name followed by a space followed by a version number
-                if (m_viewerInternal == null || m_viewerInternal.Contains(" "))
+                if (m_viewerInternal is null || m_viewerInternal.Contains(' '))
                 {
                     return m_viewerInternal;
                 }
                 else // New style version contains no spaces, just version number
                 {
-                    return Channel + " " + m_viewerInternal;
+                    return $"{Channel}  {m_viewerInternal}";
                 }
             }
         }
@@ -183,14 +183,16 @@ namespace OpenSim.Framework
         /// <returns>map of the agent circuit data</returns>
         public OSDMap PackAgentCircuitData(EntityTransferContext ctx)
         {
-            OSDMap args = new OSDMap();
-            args["agent_id"] = OSD.FromUUID(AgentID);
-            args["base_folder"] = OSD.FromUUID(BaseFolder);
-            args["caps_path"] = OSD.FromString(CapsPath);
-
-            if (ChildrenCapSeeds != null)
+            OSDMap args = new()
             {
-                OSDArray childrenSeeds = new OSDArray(ChildrenCapSeeds.Count);
+                ["agent_id"] = OSD.FromUUID(AgentID),
+                ["base_folder"] = OSD.FromUUID(BaseFolder),
+                ["caps_path"] = OSD.FromString(CapsPath)
+            };
+
+            if (ChildrenCapSeeds is not null)
+            {
+                OSDArray childrenSeeds = new(ChildrenCapSeeds.Count);
                 foreach (KeyValuePair<ulong, string> kvp in ChildrenCapSeeds)
                 {
                     OSDMap pair = new OSDMap();
diff --git a/OpenSim/Framework/AgentCircuitManager.cs b/OpenSim/Framework/AgentCircuitManager.cs
index 38fdcf83ef..060ce9542f 100644
--- a/OpenSim/Framework/AgentCircuitManager.cs
+++ b/OpenSim/Framework/AgentCircuitManager.cs
@@ -42,36 +42,38 @@ namespace OpenSim.Framework
         /// <remarks>
         /// We lock this for operations both on this dictionary and on m_agentCircuitsByUUID
         /// </remarks>
-        private ConcurrentDictionary<uint, AgentCircuitData> m_agentCircuits = new ConcurrentDictionary<uint, AgentCircuitData>();
+        private readonly ConcurrentDictionary<uint, AgentCircuitData> m_agentCircuits = new();
 
         /// <summary>
         /// Agent circuits indexed by agent UUID.
         /// </summary>
-        private ConcurrentDictionary<UUID, AgentCircuitData> m_agentCircuitsByUUID = new ConcurrentDictionary<UUID, AgentCircuitData>();
+        private readonly ConcurrentDictionary<UUID, AgentCircuitData> m_agentCircuitsByUUID = new();
 
         public virtual AuthenticateResponse AuthenticateSession(UUID sessionID, UUID agentID, uint circuitcode)
         {
-            AuthenticateResponse user = new AuthenticateResponse();
-            if (!m_agentCircuits.TryGetValue(circuitcode, out AgentCircuitData validcircuit) || validcircuit == null)
+            AuthenticateResponse user = new();
+            if (!m_agentCircuits.TryGetValue(circuitcode, out AgentCircuitData validcircuit) || validcircuit is null)
             {
                 //don't have this circuit code in our list
                 user.Authorised = false;
                 return user;
             }
 
-            if ((sessionID == validcircuit.SessionID) && (agentID == validcircuit.AgentID))
+            if (sessionID.Equals(validcircuit.SessionID) && agentID.Equals(validcircuit.AgentID))
             {
                 user.Authorised = true;
-                user.LoginInfo = new Login();
-                user.LoginInfo.Agent = agentID;
-                user.LoginInfo.Session = sessionID;
-                user.LoginInfo.SecureSession = validcircuit.SecureSessionID;
-                user.LoginInfo.First = validcircuit.firstname;
-                user.LoginInfo.Last = validcircuit.lastname;
-                user.LoginInfo.InventoryFolder = validcircuit.InventoryFolder;
-                user.LoginInfo.BaseFolder = validcircuit.BaseFolder;
-                user.LoginInfo.StartPos = validcircuit.startpos;
-                user.LoginInfo.StartFar = (float)validcircuit.startfar;
+                user.LoginInfo = new Login
+                {
+                    Agent = agentID,
+                    Session = sessionID,
+                    SecureSession = validcircuit.SecureSessionID,
+                    First = validcircuit.firstname,
+                    Last = validcircuit.lastname,
+                    InventoryFolder = validcircuit.InventoryFolder,
+                    BaseFolder = validcircuit.BaseFolder,
+                    StartPos = validcircuit.startpos,
+                    StartFar = validcircuit.startfar
+                };
             }
             else
             {
@@ -106,7 +108,7 @@ namespace OpenSim.Framework
         {
             if (m_agentCircuits.TryRemove(circuitCode, out AgentCircuitData ac))
             {
-                m_agentCircuitsByUUID.TryRemove(ac.AgentID, out AgentCircuitData dummy);
+                m_agentCircuitsByUUID.TryRemove(ac.AgentID, out AgentCircuitData _);
             }
         }
 
@@ -114,16 +116,16 @@ namespace OpenSim.Framework
         {
             if (m_agentCircuitsByUUID.TryRemove(agentID, out AgentCircuitData ac))
             {
-                m_agentCircuits.TryRemove(ac.circuitcode, out AgentCircuitData dummy);
+                m_agentCircuits.TryRemove(ac.circuitcode, out AgentCircuitData _);
             }
         }
 
         public virtual void RemoveCircuit(AgentCircuitData ac)
         {
-            m_agentCircuitsByUUID.TryRemove(ac.AgentID, out AgentCircuitData dummy);
-            m_agentCircuits.TryRemove(ac.circuitcode, out AgentCircuitData dummyb);
-            if (dummy!= null && dummy.circuitcode != ac.circuitcode) //??
-                m_agentCircuits.TryRemove(dummy.circuitcode, out AgentCircuitData dummyc);
+            m_agentCircuitsByUUID.TryRemove(ac.AgentID, out AgentCircuitData byuuid);
+            m_agentCircuits.TryRemove(ac.circuitcode, out AgentCircuitData _);
+            if (byuuid is not null && byuuid.circuitcode != ac.circuitcode) //??
+                m_agentCircuits.TryRemove(byuuid.circuitcode, out AgentCircuitData _);
         }
 
         public AgentCircuitData GetAgentCircuitData(uint circuitCode)
diff --git a/OpenSim/Framework/ClientManager.cs b/OpenSim/Framework/ClientManager.cs
index c444fcffc5..07fcc0d6d2 100644
--- a/OpenSim/Framework/ClientManager.cs
+++ b/OpenSim/Framework/ClientManager.cs
@@ -40,15 +40,15 @@ namespace OpenSim.Framework
     {
         /// <summary>A dictionary mapping from <seealso cref="UUID"/>
         /// to <seealso cref="IClientAPI"/> references</summary>
-        private readonly Dictionary<UUID, IClientAPI> m_dictbyUUID = new Dictionary<UUID, IClientAPI>();
+        private readonly Dictionary<UUID, IClientAPI> m_dictbyUUID = new();
         /// <summary>A dictionary mapping from <seealso cref="IPEndPoint"/>
         /// to <seealso cref="IClientAPI"/> references</summary>
-        private readonly Dictionary<IPEndPoint, IClientAPI> m_dictbyIPe= new Dictionary<IPEndPoint, IClientAPI>();
+        private readonly Dictionary<IPEndPoint, IClientAPI> m_dictbyIPe= new();
         /// <summary>snapshot collection of current <seealso cref="IClientAPI"/>
         /// references</summary>
         private IClientAPI[] m_array = null;
         /// <summary>Synchronization object for writing to the collections</summary>
-        private readonly object m_syncRoot = new object();
+        private readonly object m_syncRoot = new();
 
         /// <summary>Number of clients in the collection</summary>
         public int Count
@@ -96,10 +96,8 @@ namespace OpenSim.Framework
         {
             lock (m_syncRoot)
             {
-                IClientAPI value;
-                if (m_dictbyUUID.TryGetValue(key, out value))
+                if (m_dictbyUUID.Remove(key, out IClientAPI value))
                 {
-                    m_dictbyUUID.Remove(key);
                     m_dictbyIPe.Remove(value.RemoteEndPoint);
                     m_array = null;
                     return true;
diff --git a/OpenSim/Region/Framework/Scenes/SceneGraph.cs b/OpenSim/Region/Framework/Scenes/SceneGraph.cs
index cf998659ce..d196ce8ffd 100755
--- a/OpenSim/Region/Framework/Scenes/SceneGraph.cs
+++ b/OpenSim/Region/Framework/Scenes/SceneGraph.cs
@@ -37,6 +37,7 @@ using OpenSim.Framework;
 using OpenSim.Region.Framework.Scenes.Types;
 using OpenSim.Region.PhysicsModules.SharedBase;
 using OpenSim.Region.Framework.Interfaces;
+using System.Runtime.InteropServices;
 
 namespace OpenSim.Region.Framework.Scenes
 {
@@ -251,7 +252,7 @@ namespace OpenSim.Region.Framework.Scenes
                 scaleY = 1.0f / scaleY;
 
             List<ScenePresence> presences = GetScenePresences();
-            foreach (ScenePresence sp in presences)
+            foreach (ScenePresence sp in CollectionsMarshal.AsSpan(presences))
             {
                 // If this presence is a child agent, we don't want its coarse locations
                 if (sp.IsChildAgent)
@@ -804,7 +805,7 @@ namespace OpenSim.Region.Framework.Scenes
             int rootnpccount = 0;
 
             List<ScenePresence> presences = GetScenePresences();
-            foreach(ScenePresence sp in presences)
+            foreach(ScenePresence sp in CollectionsMarshal.AsSpan(presences))
             {
                 if (sp.IsChildAgent)
                     ++childcount;
@@ -986,7 +987,7 @@ namespace OpenSim.Region.Framework.Scenes
         protected internal ScenePresence GetScenePresence(in string firstName, in string lastName)
         {
             List<ScenePresence> presences = GetScenePresences();
-            foreach (ScenePresence presence in presences)
+            foreach (ScenePresence presence in CollectionsMarshal.AsSpan(presences))
             {
                 if (string.Equals(presence.Firstname, firstName, StringComparison.CurrentCultureIgnoreCase)
                     && string.Equals(presence.Lastname, lastName, StringComparison.CurrentCultureIgnoreCase))
@@ -1050,7 +1051,7 @@ namespace OpenSim.Region.Framework.Scenes
         protected internal bool TryGetAvatarByName(in string name, out ScenePresence avatar)
         {
             List<ScenePresence> presences = GetScenePresences();
-            foreach (ScenePresence presence in presences)
+            foreach (ScenePresence presence in CollectionsMarshal.AsSpan(presences))
             {
                 if (string.Equals(name, presence.ControllingClient.Name, StringComparison.CurrentCultureIgnoreCase))
                 {
@@ -1122,11 +1123,10 @@ namespace OpenSim.Region.Framework.Scenes
             float closestDistance = 280f;
             EntityIntersection result = new();
             EntityBase[] EntityList = GetEntities();
-            foreach (EntityBase ent in EntityList)
+            foreach (EntityBase ent in EntityList.AsSpan())
             {
-                if (ent is SceneObjectGroup)
+                if (ent is SceneObjectGroup reportingG)
                 {
-                    SceneObjectGroup reportingG = ent as SceneObjectGroup;
                     EntityIntersection inter = reportingG.TestIntersection(hray, frontFacesOnly, faceCenters);
                     if (inter.HitTF && inter.distance < closestDistance)
                     {
@@ -1149,7 +1149,7 @@ namespace OpenSim.Region.Framework.Scenes
             EntityBase[] entities = Entities.GetEntities();
             List<SceneObjectGroup> ret = new(entities.Length);
 
-            foreach(EntityBase et in entities)
+            foreach(EntityBase et in entities.AsSpan())
             {
                 if(et is SceneObjectGroup sog)
                     ret.Add(sog);
@@ -1188,7 +1188,7 @@ namespace OpenSim.Region.Framework.Scenes
         /// <returns>null if the part was not found</returns>
         protected internal SceneObjectGroup GetSceneObjectGroup(in string name)
         {
-            foreach(EntityBase entity in Entities.GetEntities())
+            foreach(EntityBase entity in Entities.GetEntities().AsSpan())
             {
                 if (entity is SceneObjectGroup sog && sog.Name.Equals(name))
                     return sog;
@@ -1355,7 +1355,7 @@ namespace OpenSim.Region.Framework.Scenes
         protected internal void ForEachSOG(Action<SceneObjectGroup> action)
         {
             EntityBase[] entities = Entities.GetEntities();
-            foreach (EntityBase entity in entities)
+            foreach (EntityBase entity in entities.AsSpan())
             {
                 if (entity is SceneObjectGroup sog)
                 {
@@ -1379,7 +1379,7 @@ namespace OpenSim.Region.Framework.Scenes
         public void ForEachRootScenePresence(Action<ScenePresence> action)
         {
             List<ScenePresence> presences = GetScenePresences();
-            foreach (ScenePresence sp in presences)
+            foreach (ScenePresence sp in CollectionsMarshal.AsSpan(presences))
             {
                 if(sp.IsChildAgent || sp.IsDeleted)
                     continue;
@@ -1402,7 +1402,7 @@ namespace OpenSim.Region.Framework.Scenes
         public void ForEachScenePresence(Action<ScenePresence> action)
         {
             List<ScenePresence> presences = GetScenePresences();
-            foreach (ScenePresence sp in presences)
+            foreach (ScenePresence sp in CollectionsMarshal.AsSpan(presences))
             {
                 if (sp.IsDeleted)
                     continue;
@@ -1890,10 +1890,9 @@ namespace OpenSim.Region.Framework.Scenes
                 List<SceneObjectGroup> childGroups = new();
 
                 // We do this in reverse to get the link order of the prims correct
-                for (int i = 0; i < children.Count; i++)
+                foreach (SceneObjectPart childpart in CollectionsMarshal.AsSpan(children))
                 {
-                    SceneObjectGroup child = children[i].ParentGroup;
-
+                    SceneObjectGroup child = childpart.ParentGroup;
                     // Don't try and add a group to itself - this will only cause severe problems later on.
                     if (child == parentGroup)
                         continue;
@@ -1910,7 +1909,7 @@ namespace OpenSim.Region.Framework.Scenes
                     }
                 }
 
-                foreach (SceneObjectGroup child in childGroups)
+                foreach (SceneObjectGroup child in CollectionsMarshal.AsSpan(childGroups))
                 {
                     if (parentGroup.OwnerID == child.OwnerID)
                     {
@@ -1962,7 +1961,7 @@ namespace OpenSim.Region.Framework.Scenes
             Monitor.Enter(m_linkLock);
             try
             {
-                foreach (SceneObjectPart part in prims)
+                foreach (SceneObjectPart part in CollectionsMarshal.AsSpan(prims))
                 {
                     if(part is null)
                         continue;
@@ -1997,7 +1996,7 @@ namespace OpenSim.Region.Framework.Scenes
 
                 if (childParts.Count > 0)
                 {
-                    foreach (SceneObjectPart child in childParts)
+                    foreach (SceneObjectPart child in CollectionsMarshal.AsSpan(childParts))
                     {
                         // Unlink all child parts from their groups
                         child.ParentGroup.DelinkFromGroup(child, true);
@@ -2007,7 +2006,7 @@ namespace OpenSim.Region.Framework.Scenes
                     }
                 }
 
-                foreach (SceneObjectPart root in rootParts)
+                foreach (SceneObjectPart root in CollectionsMarshal.AsSpan(rootParts))
                 {
                     // In most cases, this will run only one time, and the prim
                     // will be a solo prim
@@ -2035,7 +2034,7 @@ namespace OpenSim.Region.Framework.Scenes
                         // Determine new root
                         //
                         newSet.RemoveAt(0);
-                        foreach (SceneObjectPart newChild in newSet)
+                        foreach (SceneObjectPart newChild in CollectionsMarshal.AsSpan(newSet))
                             newChild.ClearUpdateSchedule();
 
                         LinkObjects(newRoot, newSet);
@@ -2051,7 +2050,7 @@ namespace OpenSim.Region.Framework.Scenes
 
                 // trigger events in the roots
                 //
-                foreach (SceneObjectGroup g in affectedGroups)
+                foreach (SceneObjectGroup g in CollectionsMarshal.AsSpan(affectedGroups))
                 {
                     if(g.RootPart.PhysActor is not null)
                         g.RootPart.PhysActor.Building = false;
@@ -2143,7 +2142,7 @@ namespace OpenSim.Region.Framework.Scenes
 
                         if (m_parentScene.Permissions.PropagatePermissions())
                         {
-                            foreach (SceneObjectPart child in parts)
+                            foreach (SceneObjectPart child in parts.AsSpan())
                             {
                                 child.Inventory.ChangeInventoryOwner(AgentID);
                                 child.TriggerScriptChangedEvent(Changed.OWNER);
@@ -2165,7 +2164,7 @@ namespace OpenSim.Region.Framework.Scenes
 
                         Entities.Add(copy);
                         m_scenePartsArray = null;
-                        foreach (SceneObjectPart part in parts)
+                        foreach (SceneObjectPart part in parts.AsSpan())
                         {
                             if (part.GetPrimType() == PrimType.SCULPT)
                                 m_numMesh++;