Fix CA1851

.editorconfig

@@ -834,6 +834,12 @@ dotnet_diagnostic.CA1849.severity = warning
 # Prefer static HashData method over ComputeHash. (Not available on mono)
 dotnet_diagnostic.CA1850.severity = none
 
+# Possible multiple enumerations of IEnumerable collection.
+#dotnet_code_quality.CA1851.enumeration_methods =
+#dotnet_code_quality.CA1851.linq_chain_methods =
+#dotnet_code_quality.CA1851.assume_method_enumerates_parameters = false
+dotnet_diagnostic.CA1851.severity = warning
+
 # Seal internal types.
 dotnet_diagnostic.CA1852.severity = warning
 

OpenRA.Game/GameRules/ActorInfo.cs

@@ -185,7 +185,7 @@ namespace OpenRA
 		public bool HasTraitInfo<T>() where T : ITraitInfoInterface { return traits.Contains<T>(); }
 		public T TraitInfo<T>() where T : ITraitInfoInterface { return traits.Get<T>(); }
 		public T TraitInfoOrDefault<T>() where T : ITraitInfoInterface { return traits.GetOrDefault<T>(); }
-		public IEnumerable<T> TraitInfos<T>() where T : ITraitInfoInterface { return traits.WithInterface<T>(); }
+		public IReadOnlyCollection<T> TraitInfos<T>() where T : ITraitInfoInterface { return traits.WithInterface<T>(); }
 
 		public BitSet<TargetableType> GetAllTargetTypes()
 		{

OpenRA.Game/Graphics/ChromeProvider.cs

@@ -234,7 +234,7 @@ namespace OpenRA.Graphics
 			{
 				// PERF: We don't need to search for images if there are no definitions.
 				// PERF: It's more efficient to send an empty array rather than an array of 9 nulls.
-				if (!collection.Regions.Any())
+				if (collection.Regions.Count == 0)
 					return Array.Empty<Sprite>();
 
 				// Support manual definitions for unusual dialog layouts

OpenRA.Game/Map/ActorReference.cs

@@ -139,7 +139,7 @@ namespace OpenRA
 			return removed;
 		}
 
-		public IEnumerable<T> GetAll<T>() where T : ActorInit
+		public IReadOnlyCollection<T> GetAll<T>() where T : ActorInit
 		{
 			return initDict.Value.WithInterface<T>();
 		}

OpenRA.Game/Map/CellRegion.cs

@@ -12,7 +12,6 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA
 {
@@ -64,9 +63,9 @@ namespace OpenRA
 		}
 
 		/// <summary>Returns the minimal region that covers at least the specified cells.</summary>
-		public static CellRegion BoundingRegion(MapGridType shape, IEnumerable<CPos> cells)
+		public static CellRegion BoundingRegion(MapGridType shape, IReadOnlyCollection<CPos> cells)
 		{
-			if (cells == null || !cells.Any())
+			if (cells == null || cells.Count == 0)
 				throw new ArgumentException("cells must not be null or empty.", nameof(cells));
 
 			var minU = int.MaxValue;

OpenRA.Game/Network/SyncReport.cs

@@ -201,8 +201,12 @@ namespace OpenRA.Network
 			public TypeInfo(Type type)
 			{
 				const BindingFlags Flags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
-				var fields = type.GetFields(Flags).Where(fi => !fi.IsLiteral && !fi.IsStatic && fi.HasAttribute<SyncAttribute>());
+				var fields = type.GetFields(Flags)
-				var properties = type.GetProperties(Flags).Where(pi => pi.HasAttribute<SyncAttribute>());
+					.Where(fi => !fi.IsLiteral && !fi.IsStatic && fi.HasAttribute<SyncAttribute>())
+					.ToList();
+				var properties = type.GetProperties(Flags)
+					.Where(pi => pi.HasAttribute<SyncAttribute>())
+					.ToList();
 
 				foreach (var prop in properties)
 					if (!prop.CanRead || prop.GetIndexParameters().Length > 0)

OpenRA.Game/ObjectCreator.cs

@@ -134,8 +134,8 @@ namespace OpenRA
 		public ConstructorInfo GetCtor(Type type)
 		{
 			var flags = BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance;
-			var ctors = type.GetConstructors(flags).Where(x => x.HasAttribute<UseCtorAttribute>());
+			var ctors = type.GetConstructors(flags).Where(x => x.HasAttribute<UseCtorAttribute>()).ToList();
-			if (ctors.Count() > 1)
+			if (ctors.Count > 1)
 				throw new InvalidOperationException("ObjectCreator: UseCtor on multiple constructors; invalid.");
 			return ctors.FirstOrDefault();
 		}

OpenRA.Game/Player.cs

@@ -133,7 +133,7 @@ namespace OpenRA
 
 		static FactionInfo ResolveDisplayFaction(World world, string factionName)
 		{
-			var factions = world.Map.Rules.Actors[SystemActors.World].TraitInfos<FactionInfo>().ToArray();
+			var factions = world.Map.Rules.Actors[SystemActors.World].TraitInfos<FactionInfo>();
 
 			return factions.FirstOrDefault(f => f.InternalName == factionName) ?? factions.First();
 		}

OpenRA.Game/Primitives/TypeDictionary.cs

@@ -12,14 +12,20 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA.Primitives
 {
 	public class TypeDictionary : IEnumerable<object>
 	{
-		static readonly Func<Type, List<object>> CreateList = type => new List<object>();
+		static readonly Func<Type, ITypeContainer> CreateTypeContainer = t =>
-		readonly Dictionary<Type, List<object>> data = new();
+			(ITypeContainer)typeof(TypeContainer<>).MakeGenericType(t).GetConstructor(Type.EmptyTypes).Invoke(null);
+
+		readonly Dictionary<Type, ITypeContainer> data = new();
+
+		ITypeContainer InnerGet(Type t)
+		{
+			return data.GetOrAdd(t, CreateTypeContainer);
+		}
 
 		public void Add(object val)
 		{
@@ -33,7 +39,7 @@ namespace OpenRA.Primitives
 
 		void InnerAdd(Type t, object val)
 		{
-			data.GetOrAdd(t, CreateList).Add(val);
+			InnerGet(t).Add(val);
 		}
 
 		public bool Contains<T>()
@@ -48,35 +54,33 @@ namespace OpenRA.Primitives
 
 		public T Get<T>()
 		{
-			return (T)Get(typeof(T), true);
+			return Get<T>(true);
 		}
 
 		public T GetOrDefault<T>()
 		{
-			var result = Get(typeof(T), false);
+			return Get<T>(false);
-			if (result == null)
-				return default;
-			return (T)result;
 		}
 
-		object Get(Type t, bool throwsIfMissing)
+		T Get<T>(bool throwsIfMissing)
 		{
-			if (!data.TryGetValue(t, out var ret))
+			if (!data.TryGetValue(typeof(T), out var container))
 			{
 				if (throwsIfMissing)
-					throw new InvalidOperationException($"TypeDictionary does not contain instance of type `{t}`");
+					throw new InvalidOperationException($"TypeDictionary does not contain instance of type `{typeof(T)}`");
-				return null;
+				return default;
 			}
 
-			if (ret.Count > 1)
+			var list = ((TypeContainer<T>)container).Objects;
-				throw new InvalidOperationException($"TypeDictionary contains multiple instances of type `{t}`");
+			if (list.Count > 1)
-			return ret[0];
+				throw new InvalidOperationException($"TypeDictionary contains multiple instances of type `{typeof(T)}`");
+			return list[0];
 		}
 
-		public IEnumerable<T> WithInterface<T>()
+		public IReadOnlyCollection<T> WithInterface<T>()
 		{
-			if (data.TryGetValue(typeof(T), out var objs))
+			if (data.TryGetValue(typeof(T), out var container))
-				return objs.Cast<T>();
+				return ((TypeContainer<T>)container).Objects;
 			return Array.Empty<T>();
 		}
 
@@ -92,18 +96,19 @@ namespace OpenRA.Primitives
 
 		void InnerRemove(Type t, object val)
 		{
-			if (!data.TryGetValue(t, out var objs))
+			if (!data.TryGetValue(t, out var container))
 				return;
-			objs.Remove(val);
+
-			if (objs.Count == 0)
+			container.Remove(val);
+			if (container.Count == 0)
 				data.Remove(t);
 		}
 
 		public void TrimExcess()
 		{
 			data.TrimExcess();
-			foreach (var objs in data.Values)
+			foreach (var t in data.Keys)
-				objs.TrimExcess();
+				InnerGet(t).TrimExcess();
 		}
 
 		public IEnumerator<object> GetEnumerator()
@@ -115,6 +120,36 @@ namespace OpenRA.Primitives
 		{
 			return GetEnumerator();
 		}
+
+		interface ITypeContainer
+		{
+			int Count { get; }
+			void Add(object value);
+			void Remove(object value);
+			void TrimExcess();
+		}
+
+		sealed class TypeContainer<T> : ITypeContainer
+		{
+			public List<T> Objects { get; } = new List<T>();
+
+			public int Count => Objects.Count;
+
+			public void Add(object value)
+			{
+				Objects.Add((T)value);
+			}
+
+			public void Remove(object value)
+			{
+				Objects.Remove((T)value);
+			}
+
+			public void TrimExcess()
+			{
+				Objects.TrimExcess();
+			}
+		}
 	}
 
 	public static class TypeExts

OpenRA.Game/WPos.cs

@@ -11,7 +11,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using Eluant;
 using Eluant.ObjectBinding;
 using OpenRA.Scripting;
@@ -139,20 +138,21 @@ namespace OpenRA
 	{
 		public static WPos Average(this IEnumerable<WPos> source)
 		{
-			var length = source.Count();
+			var length = 0;
-			if (length == 0)
-				return WPos.Zero;
-
 			var x = 0L;
 			var y = 0L;
 			var z = 0L;
 			foreach (var pos in source)
 			{
+				length++;
 				x += pos.X;
 				y += pos.Y;
 				z += pos.Z;
 			}
 
+			if (length == 0)
+				return WPos.Zero;
+
 			x /= length;
 			y /= length;
 			z /= length;

OpenRA.Mods.Cnc/Activities/Teleport.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System;
-using System.Linq;
 using OpenRA.Activities;
 using OpenRA.Mods.Cnc.Traits;
 using OpenRA.Mods.Common.Traits;
@@ -120,7 +119,7 @@ namespace OpenRA.Mods.Cnc.Activities
 			if (teleporter == null)
 				return null;
 
-			var restrictTo = maximumDistance == null ? null : self.World.Map.FindTilesInCircle(self.Location, maximumDistance.Value);
+			var restrictTo = maximumDistance == null ? null : self.World.Map.FindTilesInCircle(self.Location, maximumDistance.Value).ToHashSet();
 
 			if (maximumDistance != null)
 				destination = restrictTo.MinBy(x => (x - destination).LengthSquared);

OpenRA.Mods.Cnc/Traits/GpsWatcher.cs

@@ -80,7 +80,7 @@ namespace OpenRA.Mods.Cnc.Traits
 		{
 			var wasGranted = Granted;
 			var wasGrantedAllies = GrantedAllies;
-			var allyWatchers = owner.World.ActorsWithTrait<GpsWatcher>().Where(kv => kv.Actor.Owner.IsAlliedWith(owner));
+			var allyWatchers = owner.World.ActorsWithTrait<GpsWatcher>().Where(kv => kv.Actor.Owner.IsAlliedWith(owner)).ToList();
 
 			Granted = actors.Count > 0 && Launched;
 			GrantedAllies = allyWatchers.Any(w => w.Trait.Granted);

OpenRA.Mods.Cnc/Traits/SupportPowers/ChronoshiftPower.cs

@@ -358,14 +358,11 @@ namespace OpenRA.Mods.Cnc.Traits
 
 			bool IsValidTarget(CPos xy)
 			{
-				// Don't teleport if there are no units in range (either all moved out of range, or none yet moved into range)
-				var unitsInRange = power.UnitsInRange(sourceLocation);
-				if (!unitsInRange.Any())
-					return false;
-
 				var canTeleport = false;
-				foreach (var unit in unitsInRange)
+				var anyUnitsInRange = false;
+				foreach (var unit in power.UnitsInRange(sourceLocation))
 				{
+					anyUnitsInRange = true;
 					var targetCell = unit.Location + (xy - sourceLocation);
 					if (manager.Self.Owner.Shroud.IsExplored(targetCell) && unit.Trait<Chronoshiftable>().CanChronoshiftTo(unit, targetCell))
 					{
@@ -374,6 +371,10 @@ namespace OpenRA.Mods.Cnc.Traits
 					}
 				}
 
+				// Don't teleport if there are no units in range (either all moved out of range, or none yet moved into range)
+				if (!anyUnitsInRange)
+					return false;
+
 				if (!canTeleport)
 				{
 					// Check the terrain types. This will allow chronoshifts to occur on empty terrain to terrain of

OpenRA.Mods.Common/Activities/Attack.cs

@@ -196,8 +196,8 @@ namespace OpenRA.Mods.Common.Activities
 
 			// Update ranges. Exclude paused armaments except when ALL weapons are paused
 			// (e.g. out of ammo), in which case use the paused, valid weapon with highest range.
-			var activeArmaments = armaments.Where(x => !x.IsTraitPaused);
+			var activeArmaments = armaments.Where(x => !x.IsTraitPaused).ToList();
-			if (activeArmaments.Any())
+			if (activeArmaments.Count != 0)
 			{
 				minRange = activeArmaments.Max(a => a.Weapon.MinRange);
 				maxRange = activeArmaments.Min(a => a.MaxRange());

OpenRA.Mods.Common/Lint/CheckConflictingMouseBounds.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System;
-using System.Linq;
 using OpenRA.Mods.Common.Traits;
 
 namespace OpenRA.Mods.Common.Lint
@@ -21,8 +20,8 @@ namespace OpenRA.Mods.Common.Lint
 		{
 			foreach (var actorInfo in rules.Actors)
 			{
-				var selectable = actorInfo.Value.TraitInfos<SelectableInfo>().Count();
+				var selectable = actorInfo.Value.TraitInfos<SelectableInfo>().Count;
-				var interactable = actorInfo.Value.TraitInfos<InteractableInfo>().Count();
+				var interactable = actorInfo.Value.TraitInfos<InteractableInfo>().Count;
 				if (selectable > 0 && selectable != interactable)
 					emitWarning($"Actor `{actorInfo.Value.Name}` defines both Interactable and Selectable traits. This may cause unexpected results.");
 			}

OpenRA.Mods.Common/Lint/CheckDefaultVisibility.cs

@@ -37,7 +37,7 @@ namespace OpenRA.Mods.Common.Lint
 				try
 				{
 					var visibilityTypes = actorInfo.Value.TraitInfos<IDefaultVisibilityInfo>();
-					var count = visibilityTypes.Count();
+					var count = visibilityTypes.Count;
 
 					if (count == 0)
 						emitError($"Actor type `{actorInfo.Key}` does not define a default visibility type.");

OpenRA.Mods.Common/Lint/CheckHitShapes.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System;
-using System.Linq;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Server;
 using OpenRA.Traits;
@@ -41,7 +40,7 @@ namespace OpenRA.Mods.Common.Lint
 						continue;
 
 					var hitShapes = actorInfo.Value.TraitInfos<HitShapeInfo>();
-					if (!hitShapes.Any())
+					if (hitShapes.Count == 0)
 						emitError($"Actor type `{actorInfo.Key}` has a Health trait but no HitShape trait.");
 				}
 				catch (InvalidOperationException e)

OpenRA.Mods.Common/Lint/CheckLocomotorReferences.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Server;
@@ -32,12 +33,15 @@ namespace OpenRA.Mods.Common.Lint
 		static void Run(Action<string> emitError, Ruleset rules)
 		{
 			var worldActor = rules.Actors[SystemActors.World];
-			var locomotorInfos = worldActor.TraitInfos<LocomotorInfo>().ToArray();
+			var locomotorNames = worldActor.TraitInfos<LocomotorInfo>().Select(li => li.Name).ToList();
-			foreach (var li in locomotorInfos)
+			var duplicateNames = locomotorNames
-				foreach (var otherLocomotor in locomotorInfos)
+				.GroupBy(name => name)
-					if (li != otherLocomotor && li.Name == otherLocomotor.Name)
+				.Where(g => g.Count() > 1)
-						emitError($"More than one Locomotor exists with the name `{li.Name}`.");
+				.Select(g => g.Key);
+			foreach (var duplicateName in duplicateNames)
+				emitError($"More than one Locomotor exists with the name `{duplicateName}`.");
 
+			var locomotorNamesSet = locomotorNames.ToHashSet();
 			foreach (var actorInfo in rules.Actors)
 			{
 				foreach (var traitInfo in actorInfo.Value.TraitInfos<TraitInfo>())
@@ -51,16 +55,16 @@ namespace OpenRA.Mods.Common.Lint
 							if (string.IsNullOrEmpty(locomotor))
 								continue;
 
-							CheckLocomotors(actorInfo.Value, emitError, locomotorInfos, locomotor);
+							CheckLocomotors(actorInfo.Value, emitError, locomotorNamesSet, locomotor);
 						}
 					}
 				}
 			}
 		}
 
-		static void CheckLocomotors(ActorInfo actorInfo, Action<string> emitError, LocomotorInfo[] locomotorInfos, string locomotor)
+		static void CheckLocomotors(ActorInfo actorInfo, Action<string> emitError, HashSet<string> locomotorNames, string locomotor)
 		{
-			if (!locomotorInfos.Any(l => l.Name == locomotor))
+			if (!locomotorNames.Contains(locomotor))
 				emitError($"Actor `{actorInfo.Name}` defines Locomotor `{locomotor}` not found on World actor.");
 		}
 	}

OpenRA.Mods.Common/Lint/CheckSpriteBodies.cs

@@ -32,10 +32,12 @@ namespace OpenRA.Mods.Common.Lint
 		{
 			foreach (var actorInfo in rules.Actors)
 			{
-				var wsbs = actorInfo.Value.TraitInfos<WithSpriteBodyInfo>();
+				var duplicateNames = actorInfo.Value.TraitInfos<WithSpriteBodyInfo>()
-				foreach (var wsb in wsbs)
+					.GroupBy(wsb => wsb.Name)
-					if (wsbs.Any(w => w != wsb && w.Name == wsb.Name))
+					.Where(g => g.Count() > 1)
-						emitError($"Actor type `{actorInfo.Key}` has more than one *SpriteBody with Name: {wsb.Name}.");
+					.Select(g => g.Key);
+				foreach (var duplicateName in duplicateNames)
+					emitError($"Actor type `{actorInfo.Key}` has more than one *SpriteBody with Name: {duplicateName}.");
 			}
 		}
 	}

OpenRA.Mods.Common/Orders/UnitOrderGenerator.cs

@@ -50,13 +50,13 @@ namespace OpenRA.Mods.Common.Orders
 				.Where(o => o != null)
 				.ToList();
 
-			var actorsInvolved = orders.Select(o => o.Actor).Distinct();
+			var actorsInvolved = orders.Select(o => o.Actor).Distinct().ToArray();
-			if (!actorsInvolved.Any())
+			if (actorsInvolved.Length == 0)
 				yield break;
 
 			// HACK: This is required by the hacky player actions-per-minute calculation
 			// TODO: Reimplement APM properly and then remove this
-			yield return new Order("CreateGroup", actorsInvolved.First().Owner.PlayerActor, false, actorsInvolved.ToArray());
+			yield return new Order("CreateGroup", actorsInvolved.First().Owner.PlayerActor, false, actorsInvolved);
 
 			foreach (var o in orders)
 				yield return CheckSameOrder(o.Order, o.Trait.IssueOrder(o.Actor, o.Order, o.Target, mi.Modifiers.HasModifier(Modifiers.Shift)));
@@ -165,7 +165,8 @@ namespace OpenRA.Mods.Common.Orders
 			var orders = self.TraitsImplementing<IIssueOrder>()
 				.SelectMany(trait => trait.Orders.Select(x => new { Trait = trait, Order = x }))
 				.Select(x => x)
-				.OrderByDescending(x => x.Order.OrderPriority);
+				.OrderByDescending(x => x.Order.OrderPriority)
+				.ToList();
 
 			for (var i = 0; i < 2; i++)
 			{

OpenRA.Mods.Common/Scripting/Properties/ProductionProperties.cs

@@ -245,7 +245,7 @@ namespace OpenRA.Mods.Common.Scripting
 			foreach (var actorType in actorTypes.Distinct())
 				typeToQueueMap.Add(actorType, GetBuildableInfo(actorType).Queue.First());
 
-			var queueTypes = typeToQueueMap.Values.Distinct();
+			var queueTypes = typeToQueueMap.Values.Distinct().ToList();
 
 			if (queueTypes.Any(t => !queues.ContainsKey(t) || productionHandlers.ContainsKey(t)))
 				return false;

OpenRA.Mods.Common/ServerTraits/LobbyCommands.cs

@@ -748,10 +748,11 @@ namespace OpenRA.Mods.Common.Server
 				teamCount = teamCount.Clamp(0, maxTeams);
 				var clients = server.LobbyInfo.Slots
 					.Select(slot => server.LobbyInfo.ClientInSlot(slot.Key))
-					.Where(c => c != null && !server.LobbyInfo.Slots[c.Slot].LockTeam);
+					.Where(c => c != null && !server.LobbyInfo.Slots[c.Slot].LockTeam)
+					.ToList();
 
 				var assigned = 0;
-				var clientCount = clients.Count();
+				var clientCount = clients.Count;
 				foreach (var player in clients)
 				{
 					// Free for all

OpenRA.Mods.Common/Traits/AppearsOnMapPreview.cs

@@ -41,8 +41,8 @@ namespace OpenRA.Mods.Common.Traits
 			else
 			{
 				var owner = map.PlayerDefinitions.Single(p => s.Get<OwnerInit>().InternalName == p.Value.Nodes.Last(k => k.Key == "Name").Value.Value);
-				var colorValue = owner.Value.Nodes.Where(n => n.Key == "Color");
+				var colorValue = owner.Value.Nodes.FirstOrDefault(n => n.Key == "Color");
-				var ownerColor = colorValue.Any() ? colorValue.First().Value.Value : "FFFFFF";
+				var ownerColor = colorValue?.Value.Value ?? "FFFFFF";
 				Color.TryParse(ownerColor, out color);
 			}
 

OpenRA.Mods.Common/Traits/Attack/AttackBase.cs

@@ -445,15 +445,15 @@ namespace OpenRA.Mods.Common.Traits
 					modifiers |= TargetModifiers.ForceAttack;
 
 				var forceAttack = modifiers.HasModifier(TargetModifiers.ForceAttack);
-				var armaments = ab.ChooseArmamentsForTarget(target, forceAttack);
-				if (!armaments.Any())
-					return false;
 
 				// Use valid armament with highest range out of those that have ammo
 				// If all are out of ammo, just use valid armament with highest range
-				armaments = armaments.OrderByDescending(x => x.MaxRange());
+				var a = ab.ChooseArmamentsForTarget(target, forceAttack)
-				var a = armaments.FirstOrDefault(x => !x.IsTraitPaused);
+					.OrderBy(x => x.IsTraitPaused)
-				a ??= armaments.First();
+					.ThenByDescending(x => x.MaxRange())
+					.FirstOrDefault();
+				if (a == null)
+					return false;
 
 				var outOfRange = !target.IsInRange(self.CenterPosition, a.MaxRange()) ||
 					(!forceAttack && target.Type == TargetType.FrozenActor && !ab.Info.TargetFrozenActors);
@@ -482,15 +482,15 @@ namespace OpenRA.Mods.Common.Traits
 					return false;
 
 				var target = Target.FromCell(self.World, location);
-				var armaments = ab.ChooseArmamentsForTarget(target, true);
-				if (!armaments.Any())
-					return false;
 
 				// Use valid armament with highest range out of those that have ammo
 				// If all are out of ammo, just use valid armament with highest range
-				armaments = armaments.OrderByDescending(x => x.MaxRange());
+				var a = ab.ChooseArmamentsForTarget(target, true)
-				var a = armaments.FirstOrDefault(x => !x.IsTraitPaused);
+					.OrderBy(x => x.IsTraitPaused)
-				a ??= armaments.First();
+					.ThenByDescending(x => x.MaxRange())
+					.FirstOrDefault();
+				if (a == null)
+					return false;
 
 				cursor = !target.IsInRange(self.CenterPosition, a.MaxRange())
 					? ab.Info.OutsideRangeCursor ?? a.Info.OutsideRangeCursor

OpenRA.Mods.Common/Traits/BotModules/Squads/AttackOrFleeFuzzy.cs

@@ -163,7 +163,7 @@ namespace OpenRA.Mods.Common.Traits.BotModules.Squads
 			fuzzyEngine.Rules.Add(fuzzyEngine.ParseRule(rule));
 		}
 
-		public bool CanAttack(IEnumerable<Actor> ownUnits, IEnumerable<Actor> enemyUnits)
+		public bool CanAttack(IReadOnlyCollection<Actor> ownUnits, IReadOnlyCollection<Actor> enemyUnits)
 		{
 			double attackChance;
 			var inputValues = new Dictionary<FuzzyVariable, double>();
@@ -201,7 +201,7 @@ namespace OpenRA.Mods.Common.Traits.BotModules.Squads
 			return (int)((long)sumOfHp * normalizeByValue / sumOfMaxHp);
 		}
 
-		static float RelativePower(IEnumerable<Actor> own, IEnumerable<Actor> enemy)
+		static float RelativePower(IReadOnlyCollection<Actor> own, IReadOnlyCollection<Actor> enemy)
 		{
 			return RelativeValue(own, enemy, 100, SumOfValues<AttackBaseInfo>, a =>
 			{
@@ -225,18 +225,18 @@ namespace OpenRA.Mods.Common.Traits.BotModules.Squads
 			});
 		}
 
-		static float RelativeSpeed(IEnumerable<Actor> own, IEnumerable<Actor> enemy)
+		static float RelativeSpeed(IReadOnlyCollection<Actor> own, IReadOnlyCollection<Actor> enemy)
 		{
 			return RelativeValue(own, enemy, 100, Average<MobileInfo>, (Actor a) => a.Info.TraitInfo<MobileInfo>().Speed);
 		}
 
-		static float RelativeValue(IEnumerable<Actor> own, IEnumerable<Actor> enemy, float normalizeByValue,
+		static float RelativeValue(IReadOnlyCollection<Actor> own, IReadOnlyCollection<Actor> enemy, float normalizeByValue,
-					Func<IEnumerable<Actor>, Func<Actor, int>, float> relativeFunc, Func<Actor, int> getValue)
+					Func<IReadOnlyCollection<Actor>, Func<Actor, int>, float> relativeFunc, Func<Actor, int> getValue)
 		{
-			if (!enemy.Any())
+			if (enemy.Count == 0)
 				return 999.0f;
 
-			if (!own.Any())
+			if (own.Count == 0)
 				return 0.0f;
 
 			var relative = relativeFunc(own, getValue) / relativeFunc(enemy, getValue) * normalizeByValue;

OpenRA.Mods.Common/Traits/BotModules/Squads/States/AirStates.cs

@@ -22,9 +22,9 @@ namespace OpenRA.Mods.Common.Traits.BotModules.Squads
 
 		protected const int MissileUnitMultiplier = 3;
 
-		protected static int CountAntiAirUnits(IEnumerable<Actor> units)
+		protected static int CountAntiAirUnits(IReadOnlyCollection<Actor> units)
 		{
-			if (!units.Any())
+			if (units.Count == 0)
 				return 0;
 
 			var missileUnitsCount = 0;

OpenRA.Mods.Common/Traits/BotModules/Squads/States/StateBase.cs

@@ -80,7 +80,7 @@ namespace OpenRA.Mods.Common.Traits.BotModules.Squads
 			return false;
 		}
 
-		protected virtual bool ShouldFlee(Squad squad, Func<IEnumerable<Actor>, bool> flee)
+		protected virtual bool ShouldFlee(Squad squad, Func<IReadOnlyCollection<Actor>, bool> flee)
 		{
 			if (!squad.IsValid)
 				return false;
@@ -95,8 +95,10 @@ namespace OpenRA.Mods.Common.Traits.BotModules.Squads
 				if (u.Owner == squad.Bot.Player && u.Info.HasTraitInfo<BuildingInfo>())
 					return false;
 
-			var enemyAroundUnit = units.Where(unit => squad.SquadManager.IsPreferredEnemyUnit(unit) && unit.Info.HasTraitInfo<AttackBaseInfo>());
+			var enemyAroundUnit = units
-			if (!enemyAroundUnit.Any())
+				.Where(unit => squad.SquadManager.IsPreferredEnemyUnit(unit) && unit.Info.HasTraitInfo<AttackBaseInfo>())
+				.ToList();
+			if (enemyAroundUnit.Count == 0)
 				return false;
 
 			return flee(enemyAroundUnit);

OpenRA.Mods.Common/Traits/BotModules/UnitBuilderBotModule.cs

@@ -172,17 +172,18 @@ namespace OpenRA.Mods.Common.Traits
 
 		ActorInfo ChooseUnitToBuild(ProductionQueue queue)
 		{
-			var buildableThings = queue.BuildableItems();
+			var buildableThings = queue.BuildableItems().Select(b => b.Name).ToHashSet();
-			if (!buildableThings.Any())
+			if (buildableThings.Count == 0)
 				return null;
 
 			var myUnits = player.World
 				.ActorsHavingTrait<IPositionable>()
 				.Where(a => a.Owner == player)
-				.Select(a => a.Info.Name).ToList();
+				.Select(a => a.Info.Name)
+				.ToList();
 
 			foreach (var unit in Info.UnitsToBuild.Shuffle(world.LocalRandom))
-				if (buildableThings.Any(b => b.Name == unit.Key))
+				if (buildableThings.Contains(unit.Key))
 					if (myUnits.Count(a => a == unit.Key) * 100 < unit.Value * myUnits.Count)
 						if (HasAdequateAirUnitReloadBuildings(world.Map.Rules.Actors[unit.Key]))
 							return world.Map.Rules.Actors[unit.Key];

OpenRA.Mods.Common/Traits/Buildings/Exit.cs

@@ -80,9 +80,6 @@ namespace OpenRA.Mods.Common.Traits
 				return null;
 
 			var allOfType = Exits(actor, productionType);
-			if (!allOfType.Any())
-				return null;
-
 			foreach (var g in allOfType.GroupBy(e => e.Info.Priority))
 			{
 				var shuffled = g.Shuffle(world.SharedRandom);

OpenRA.Mods.Common/Traits/Buildings/TransformsIntoMobile.cs

@@ -54,13 +54,15 @@ namespace OpenRA.Mods.Common.Traits
 
 		public override void RulesetLoaded(Ruleset rules, ActorInfo ai)
 		{
-			var locomotorInfos = rules.Actors[SystemActors.World].TraitInfos<LocomotorInfo>();
+			var locomotorInfos = rules.Actors[SystemActors.World].TraitInfos<LocomotorInfo>()
-			LocomotorInfo = locomotorInfos.FirstOrDefault(li => li.Name == Locomotor);
+				.Where(li => li.Name == Locomotor).ToList();
-			if (LocomotorInfo == null)
+			if (locomotorInfos.Count == 0)
 				throw new YamlException($"A locomotor named '{Locomotor}' doesn't exist.");
-			else if (locomotorInfos.Count(li => li.Name == Locomotor) > 1)
+			else if (locomotorInfos.Count > 1)
 				throw new YamlException($"There is more than one locomotor named '{Locomotor}'.");
 
+			LocomotorInfo = locomotorInfos[0];
+
 			base.RulesetLoaded(rules, ai);
 		}
 	}

OpenRA.Mods.Common/Traits/Crates/Crate.cs

@@ -113,23 +113,32 @@ namespace OpenRA.Mods.Common.Traits
 		void INotifyParachute.OnLanded(Actor self)
 		{
 			// Check whether the crate landed on anything
-			var landedOn = self.World.ActorMap.GetActorsAt(self.Location)
+			var anyOtherActors = false;
-				.Where(a => a != self);
+			Actor collector = null;
-
+			foreach (var otherActor in self.World.ActorMap.GetActorsAt(self.Location))
-			if (!landedOn.Any())
-				return;
-
-			var collector = landedOn.FirstOrDefault(a =>
 			{
+				if (self == otherActor)
+					continue;
+
+				anyOtherActors = true;
+
 				// Mobile is (currently) the only trait that supports crushing
-				var mi = a.Info.TraitInfoOrDefault<MobileInfo>();
+				var mi = otherActor.Info.TraitInfoOrDefault<MobileInfo>();
 				if (mi == null)
-					return false;
+					continue;
 
 				// Make sure that the actor can collect this crate type
 				// Crate can only be crushed if it is not in the air.
-				return self.IsAtGroundLevel() && mi.LocomotorInfo.Crushes.Contains(info.CrushClass);
+				if (self.IsAtGroundLevel() && mi.LocomotorInfo.Crushes.Contains(info.CrushClass))
-			});
+				{
+					collector = otherActor;
+					break;
+				}
+			}
+
+			// The crate can land unhindered.
+			if (!anyOtherActors)
+				return;
 
 			// Destroy the crate if none of the units in the cell are valid collectors
 			if (collector != null)
@@ -148,10 +157,11 @@ namespace OpenRA.Mods.Common.Traits
 			self.Dispose();
 			collected = true;
 
-			if (crateActions.Any())
+			var shares = crateActions
+				.Select(a => (Action: a, Shares: a.GetSelectionSharesOuter(crusher)))
+				.ToList();
+			if (shares.Count != 0)
 			{
-				var shares = crateActions.Select(a => (Action: a, Shares: a.GetSelectionSharesOuter(crusher)));
-
 				var totalShares = shares.Sum(a => a.Shares);
 				var n = self.World.SharedRandom.Next(totalShares);
 

OpenRA.Mods.Common/Traits/Crates/GrantExternalConditionCrateAction.cs

@@ -76,7 +76,8 @@ namespace OpenRA.Mods.Common.Traits
 		void GrantCondition(Actor actor)
 		{
 			var externals = actor.TraitsImplementing<ExternalCondition>()
-				.Where(t => t.Info.Condition == info.Condition);
+				.Where(t => t.Info.Condition == info.Condition)
+				.ToList();
 
 			ExternalCondition external = null;
 			for (var n = 0; n < info.Levels; n++)

OpenRA.Mods.Common/Traits/Mobile.cs

@@ -104,13 +104,15 @@ namespace OpenRA.Mods.Common.Traits
 
 		public override void RulesetLoaded(Ruleset rules, ActorInfo ai)
 		{
-			var locomotorInfos = rules.Actors[SystemActors.World].TraitInfos<LocomotorInfo>();
+			var locomotorInfos = rules.Actors[SystemActors.World].TraitInfos<LocomotorInfo>()
-			LocomotorInfo = locomotorInfos.FirstOrDefault(li => li.Name == Locomotor);
+				.Where(li => li.Name == Locomotor).ToList();
-			if (LocomotorInfo == null)
+			if (locomotorInfos.Count == 0)
 				throw new YamlException($"A locomotor named '{Locomotor}' doesn't exist.");
-			else if (locomotorInfos.Count(li => li.Name == Locomotor) > 1)
+			else if (locomotorInfos.Count > 1)
 				throw new YamlException($"There is more than one locomotor named '{Locomotor}'.");
 
+			LocomotorInfo = locomotorInfos[0];
+
 			// We need to reset the reference to the locomotor between each worlds, otherwise we are reference the previous state.
 			locomotor = null;
 

OpenRA.Mods.Common/Traits/Player/ClassicParallelProductionQueue.cs

@@ -133,15 +133,15 @@ namespace OpenRA.Mods.Common.Traits
 
 		public override TraitPair<Production> MostLikelyProducer()
 		{
-			var productionActors = self.World.ActorsWithTrait<Production>()
+			var productionActor = self.World.ActorsWithTrait<Production>()
 				.Where(x => x.Actor.Owner == self.Owner
 					&& !x.Trait.IsTraitDisabled && x.Trait.Info.Produces.Contains(Info.Type))
-				.OrderByDescending(x => x.Actor.IsPrimaryBuilding())
+				.OrderBy(x => x.Trait.IsTraitPaused)
+				.ThenByDescending(x => x.Actor.IsPrimaryBuilding())
 				.ThenByDescending(x => x.Actor.ActorID)
-				.ToList();
+				.FirstOrDefault();
 
-			var unpaused = productionActors.FirstOrDefault(a => !a.Trait.IsTraitPaused);
+			return productionActor;
-			return unpaused.Trait != null ? unpaused : productionActors.FirstOrDefault();
 		}
 
 		protected override bool BuildUnit(ActorInfo unit)
@@ -159,14 +159,10 @@ namespace OpenRA.Mods.Common.Traits
 				.OrderByDescending(x => x.Actor.IsPrimaryBuilding())
 				.ThenByDescending(x => x.Actor.ActorID);
 
-			if (!producers.Any())
+			var anyProducers = false;
-			{
-				CancelProduction(unit.Name, 1);
-				return false;
-			}
-
 			foreach (var p in producers)
 			{
+				anyProducers = true;
 				if (p.Trait.IsTraitPaused)
 					continue;
 
@@ -184,6 +180,12 @@ namespace OpenRA.Mods.Common.Traits
 				}
 			}
 
+			if (!anyProducers)
+			{
+				CancelProduction(unit.Name, 1);
+				return false;
+			}
+
 			return false;
 		}
 

OpenRA.Mods.Common/Traits/Player/ClassicProductionQueue.cs

@@ -83,15 +83,15 @@ namespace OpenRA.Mods.Common.Traits
 
 		public override TraitPair<Production> MostLikelyProducer()
 		{
-			var productionActors = self.World.ActorsWithTrait<Production>()
+			var productionActor = self.World.ActorsWithTrait<Production>()
 				.Where(x => x.Actor.Owner == self.Owner
 					&& !x.Trait.IsTraitDisabled && x.Trait.Info.Produces.Contains(Info.Type))
-				.OrderByDescending(x => x.Actor.IsPrimaryBuilding())
+				.OrderBy(x => x.Trait.IsTraitPaused)
+				.ThenByDescending(x => x.Actor.IsPrimaryBuilding())
 				.ThenByDescending(x => x.Actor.ActorID)
-				.ToList();
+				.FirstOrDefault();
 
-			var unpaused = productionActors.FirstOrDefault(a => !a.Trait.IsTraitPaused);
+			return productionActor;
-			return unpaused.Trait != null ? unpaused : productionActors.FirstOrDefault();
 		}
 
 		protected override bool BuildUnit(ActorInfo unit)
@@ -109,14 +109,10 @@ namespace OpenRA.Mods.Common.Traits
 					.OrderByDescending(x => x.Actor.IsPrimaryBuilding())
 					.ThenByDescending(x => x.Actor.ActorID);
 
-			if (!producers.Any())
+			var anyProducers = false;
-			{
-				CancelProduction(unit.Name, 1);
-				return false;
-			}
-
 			foreach (var p in producers)
 			{
+				anyProducers = true;
 				if (p.Trait.IsTraitPaused)
 					continue;
 
@@ -134,6 +130,12 @@ namespace OpenRA.Mods.Common.Traits
 				}
 			}
 
+			if (!anyProducers)
+			{
+				CancelProduction(unit.Name, 1);
+				return false;
+			}
+
 			return false;
 		}
 

OpenRA.Mods.Common/Traits/Player/ConquestVictoryConditions.cs

@@ -81,13 +81,14 @@ namespace OpenRA.Mods.Common.Traits
 				return;
 
 			var myTeam = self.World.LobbyInfo.ClientWithIndex(self.Owner.ClientIndex).Team;
-			var teams = self.World.Players.Where(p => !p.NonCombatant && p.Playable)
+			var victoriousTeam = self.World.Players.Where(p => !p.NonCombatant && p.Playable)
 				.Select(p => (Player: p, PlayerStatistics: p.PlayerActor.TraitOrDefault<PlayerStatistics>()))
 				.OrderByDescending(p => p.PlayerStatistics?.Experience ?? 0)
 				.GroupBy(p => (self.World.LobbyInfo.ClientWithIndex(p.Player.ClientIndex) ?? new Session.Client()).Team)
-				.OrderByDescending(g => g.Sum(gg => gg.PlayerStatistics?.Experience ?? 0));
+				.OrderByDescending(g => g.Sum(gg => gg.PlayerStatistics?.Experience ?? 0))
+				.First();
 
-			if (teams.First().Key == myTeam && (myTeam != 0 || teams.First().First().Player == self.Owner))
+			if (victoriousTeam.Key == myTeam && (myTeam != 0 || victoriousTeam.First().Player == self.Owner))
 			{
 				mo.MarkCompleted(self.Owner, objectiveID);
 				return;

OpenRA.Mods.Common/Traits/Player/ProductionQueue.cs

@@ -594,9 +594,11 @@ namespace OpenRA.Mods.Common.Traits
 		// Returns the actor/trait that is most likely (but not necessarily guaranteed) to produce something in this queue
 		public virtual TraitPair<Production> MostLikelyProducer()
 		{
-			var traits = productionTraits.Where(p => !p.IsTraitDisabled && p.Info.Produces.Contains(Info.Type));
+			var trait = productionTraits
-			var unpaused = traits.FirstOrDefault(a => !a.IsTraitPaused);
+				.Where(p => !p.IsTraitDisabled && p.Info.Produces.Contains(Info.Type))
-			return new TraitPair<Production>(Actor, unpaused ?? traits.FirstOrDefault());
+				.OrderBy(p => p.IsTraitPaused)
+				.FirstOrDefault();
+			return new TraitPair<Production>(Actor, trait);
 		}
 
 		// Builds a unit from the actor that holds this queue (1 queue per building)

OpenRA.Mods.Common/Traits/Player/StrategicVictoryConditions.cs

@@ -89,13 +89,21 @@ namespace OpenRA.Mods.Common.Traits
 			if (!self.Owner.NonCombatant && self.Owner.HasNoRequiredUnits(shortGame))
 				mo.MarkFailed(self.Owner, objectiveID);
 
-			var others = self.World.Players.Where(p => !p.NonCombatant
+			var allOthersLost = true;
-				&& !p.IsAlliedWith(self.Owner));
+			var anyOtherWon = false;
+			foreach (var other in self.World.Players)
+			{
+				if (other.NonCombatant || other.IsAlliedWith(self.Owner))
+					continue;
 
-			if (others.All(p => p.WinState == WinState.Lost))
+				allOthersLost = allOthersLost && other.WinState == WinState.Lost;
+				anyOtherWon = anyOtherWon || other.WinState == WinState.Won;
+			}
+
+			if (allOthersLost)
 				mo.MarkCompleted(player, objectiveID);
 
-			if (others.Any(p => p.WinState == WinState.Won))
+			if (anyOtherWon)
 				mo.MarkFailed(player, objectiveID);
 
 			// See if any of the conditions are met to increase the count
@@ -119,13 +127,14 @@ namespace OpenRA.Mods.Common.Traits
 				return;
 
 			var myTeam = self.World.LobbyInfo.ClientWithIndex(self.Owner.ClientIndex).Team;
-			var teams = self.World.Players.Where(p => !p.NonCombatant && p.Playable)
+			var victoriousTeam = self.World.Players.Where(p => !p.NonCombatant && p.Playable)
 				.Select(p => (Player: p, PlayerStatistics: p.PlayerActor.TraitOrDefault<PlayerStatistics>()))
 				.OrderByDescending(p => p.PlayerStatistics?.Experience ?? 0)
 				.GroupBy(p => (self.World.LobbyInfo.ClientWithIndex(p.Player.ClientIndex) ?? new Session.Client()).Team)
-				.OrderByDescending(g => g.Sum(gg => gg.PlayerStatistics?.Experience ?? 0));
+				.OrderByDescending(g => g.Sum(gg => gg.PlayerStatistics?.Experience ?? 0))
+				.First();
 
-			if (teams.First().Key == myTeam && (myTeam != 0 || teams.First().First().Player == self.Owner))
+			if (victoriousTeam.Key == myTeam && (myTeam != 0 || victoriousTeam.First().Player == self.Owner))
 			{
 				mo.MarkCompleted(self.Owner, objectiveID);
 				return;

OpenRA.Mods.Common/Traits/RejectsOrders.cs

@@ -44,10 +44,19 @@ namespace OpenRA.Mods.Common.Traits
 			if (rejectsOrdersTraits.Length == 0)
 				return true;
 
-			var reject = rejectsOrdersTraits.SelectMany(t => t.Reject);
+			foreach (var rejectsOrdersTrait in rejectsOrdersTraits)
-			var except = rejectsOrdersTraits.SelectMany(t => t.Except);
+				if (rejectsOrdersTrait.Except.Contains(orderString))
+					return true;
 
-			return except.Contains(orderString) || (reject.Any() && !reject.Contains(orderString));
+			var anyRejects = false;
+			foreach (var rejectsOrdersTrait in rejectsOrdersTraits)
+			{
+				anyRejects = anyRejects || rejectsOrdersTrait.Reject.Count > 0;
+				if (rejectsOrdersTrait.Reject.Contains(orderString))
+					return false;
+			}
+
+			return anyRejects;
 		}
 	}
 }

OpenRA.Mods.Common/Traits/Render/WithShadow.cs

@@ -51,29 +51,27 @@ namespace OpenRA.Mods.Common.Traits.Render
 			if (IsTraitDisabled)
 				return r;
 
+			var renderables = r.ToList();
 			var height = self.World.Map.DistanceAboveTerrain(self.CenterPosition).Length;
-			var shadowSprites = r.Where(s => !s.IsDecoration && s is IModifyableRenderable)
+			var shadowSprites = renderables.Where(s => !s.IsDecoration && s is IModifyableRenderable)
 				.Select(ma => ((IModifyableRenderable)ma).WithTint(shadowColor, ((IModifyableRenderable)ma).TintModifiers | TintModifiers.ReplaceColor)
 					.WithAlpha(shadowAlpha)
 					.OffsetBy(info.Offset - new WVec(0, 0, height))
 					.WithZOffset(ma.ZOffset + height + info.ZOffset)
 					.AsDecoration());
 
-			return shadowSprites.Concat(r);
+			return shadowSprites.Concat(renderables);
 		}
 
 		IEnumerable<Rectangle> IRenderModifier.ModifyScreenBounds(Actor self, WorldRenderer wr, IEnumerable<Rectangle> bounds)
 		{
-			foreach (var r in bounds)
-				yield return r;
-
 			if (IsTraitDisabled)
-				yield break;
+				return bounds;
 
+			var boundsList = bounds.ToList();
 			var height = self.World.Map.DistanceAboveTerrain(self.CenterPosition).Length;
 			var offset = wr.ScreenPxOffset(info.Offset - new WVec(0, 0, height));
-			foreach (var r in bounds)
+			return boundsList.Concat(boundsList.Select(r => new Rectangle(r.X + offset.X, r.Y + offset.Y, r.Width, r.Height)));
-				yield return new Rectangle(r.X + offset.X, r.Y + offset.Y, r.Width, r.Height);
 		}
 	}
 }

OpenRA.Mods.Common/Traits/World/ActorMap.cs

@@ -205,8 +205,8 @@ namespace OpenRA.Mods.Common.Traits
 			actorShouldBeRemoved = removeActorPosition.Contains;
 
 			LargestActorRadius = map.Rules.Actors.SelectMany(a => a.Value.TraitInfos<HitShapeInfo>()).Max(h => h.Type.OuterRadius);
-			var blockers = map.Rules.Actors.Where(a => a.Value.HasTraitInfo<IBlocksProjectilesInfo>());
+			var blockers = map.Rules.Actors.Where(a => a.Value.HasTraitInfo<IBlocksProjectilesInfo>()).ToList();
-			LargestBlockingActorRadius = blockers.Any() ? blockers.SelectMany(a => a.Value.TraitInfos<HitShapeInfo>()).Max(h => h.Type.OuterRadius) : WDist.Zero;
+			LargestBlockingActorRadius = blockers.Count != 0 ? blockers.SelectMany(a => a.Value.TraitInfos<HitShapeInfo>()).Max(h => h.Type.OuterRadius) : WDist.Zero;
 		}
 
 		void INotifyCreated.Created(Actor self)

OpenRA.Mods.Common/Traits/World/CreateMapPlayers.cs

@@ -28,7 +28,7 @@ namespace OpenRA.Mods.Common.Traits
 		/// </summary>
 		void ICreatePlayersInfo.CreateServerPlayers(MapPreview map, Session lobbyInfo, List<GameInformation.Player> players, MersenneTwister playerRandom)
 		{
-			var factions = map.WorldActorInfo.TraitInfos<FactionInfo>().ToArray();
+			var factions = map.WorldActorInfo.TraitInfos<FactionInfo>();
 			var assignSpawnLocations = map.WorldActorInfo.TraitInfoOrDefault<IAssignSpawnPointsInfo>();
 			var spawnState = assignSpawnLocations?.InitializeState(map, lobbyInfo);
 
@@ -41,7 +41,7 @@ namespace OpenRA.Mods.Common.Traits
 			}
 
 			// Create the regular playable players.
-			var bots = map.PlayerActorInfo.TraitInfos<IBotInfo>().ToArray();
+			var bots = map.PlayerActorInfo.TraitInfos<IBotInfo>();
 
 			foreach (var kv in lobbyInfo.Slots)
 			{

OpenRA.Mods.Common/Traits/World/EditorActorPreview.cs

@@ -178,7 +178,7 @@ namespace OpenRA.Mods.Common.Traits
 			return reference.GetOrDefault<T>(info);
 		}
 
-		public IEnumerable<T> GetInits<T>() where T : ActorInit
+		public IReadOnlyCollection<T> GetInits<T>() where T : ActorInit
 		{
 			return reference.GetAll<T>();
 		}

OpenRA.Mods.Common/Traits/World/Locomotor.cs

@@ -136,7 +136,7 @@ namespace OpenRA.Mods.Common.Traits
 			public readonly LongBitSet<PlayerBitMask> Crushable;
 			public readonly CellFlag CellFlag;
 
-			public CellCache(LongBitSet<PlayerBitMask> immovable, CellFlag cellFlag, LongBitSet<PlayerBitMask> crushable = default)
+			public CellCache(LongBitSet<PlayerBitMask> immovable, CellFlag cellFlag, LongBitSet<PlayerBitMask> crushable)
 			{
 				Immovable = immovable;
 				Crushable = crushable;
@@ -459,26 +459,17 @@ namespace OpenRA.Mods.Common.Traits
 			using (new PerfSample("locomotor_cache"))
 			{
 				var cache = blockingCache[cell.Layer];
-
-				var actors = actorMap.GetActorsAt(cell);
 				var cellFlag = CellFlag.HasFreeSpace;
-
-				if (!actors.Any())
-				{
-					cache[cell] = new CellCache(default, cellFlag);
-					return;
-				}
-
-				if (sharesCell && actorMap.HasFreeSubCell(cell))
-				{
-					cache[cell] = new CellCache(default, cellFlag);
-					return;
-				}
-
 				var cellImmovablePlayers = default(LongBitSet<PlayerBitMask>);
 				var cellCrushablePlayers = world.AllPlayersMask;
 
-				foreach (var actor in actors)
+				if (sharesCell && actorMap.HasFreeSubCell(cell))
+				{
+					cache[cell] = new CellCache(cellImmovablePlayers, cellFlag, cellCrushablePlayers);
+					return;
+				}
+
+				foreach (var actor in actorMap.GetActorsAt(cell))
 				{
 					var actorImmovablePlayers = world.AllPlayersMask;
 					var actorCrushablePlayers = world.NoPlayersMask;
@@ -493,11 +484,10 @@ namespace OpenRA.Mods.Common.Traits
 					if (isTransitOnly)
 						cellFlag |= CellFlag.HasTransitOnlyActor;
 
-					if (crushables.Any())
+					foreach (var crushable in crushables)
 					{
 						cellFlag |= CellFlag.HasCrushableActor;
-						foreach (var crushable in crushables)
+						actorCrushablePlayers = actorCrushablePlayers.Union(crushable.CrushableBy(actor, Info.Crushes));
-							actorCrushablePlayers = actorCrushablePlayers.Union(crushable.CrushableBy(actor, Info.Crushes));
 					}
 
 					if (isMoving)

OpenRA.Mods.Common/UpdateRules/Rules/20210321/UnhardcodeVeteranProductionIconOverlay.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System.Collections.Generic;
-using System.Linq;
 
 namespace OpenRA.Mods.Common.UpdateRules.Rules
 {
@@ -24,7 +23,7 @@ namespace OpenRA.Mods.Common.UpdateRules.Rules
 
 		public override IEnumerable<string> AfterUpdate(ModData modData)
 		{
-			if (locations.Any())
+			if (locations.Count != 0)
 				yield return "Icon overlay logic has been split from ProducibleWithLevel to WithProductionIconOverlay trait.\n" +
 					"If you have been using VeteranProductionIconOverlay trait, add WithProductionIconOverlay to following actors:\n" +
 					UpdateUtils.FormatMessageList(locations);

OpenRA.Mods.Common/UpdateRules/Rules/20230225/ExplicitSequenceFilenames.cs

@@ -45,16 +45,16 @@ namespace OpenRA.Mods.Common.UpdateRules.Rules
 				foreach (var sequenceNode in imageNode.Value.Nodes)
 				{
 					var useTilesetExtensionNode = sequenceNode.LastChildMatching("UseTilesetExtension");
-					if (useTilesetExtensionNode != null && !tilesetExtensions.Any())
+					if (useTilesetExtensionNode != null && tilesetExtensions.Count == 0)
 						requiredMetadata.Add("TilesetExtensions");
 
 					var useTilesetCodeNode = sequenceNode.LastChildMatching("UseTilesetCode");
-					if (useTilesetCodeNode != null && !tilesetCodes.Any())
+					if (useTilesetCodeNode != null && tilesetCodes.Count == 0)
 						requiredMetadata.Add("TilesetCodes");
 				}
 			}
 
-			if (requiredMetadata.Any())
+			if (requiredMetadata.Count != 0)
 			{
 				yield return $"The ExplicitSequenceFilenames rule requires {requiredMetadata.JoinWith(", ")}\n" +
 				             "to be defined under the SpriteSequenceFormat definition in mod.yaml.\n" +
@@ -317,7 +317,7 @@ namespace OpenRA.Mods.Common.UpdateRules.Rules
 						if (allSequencesHaveTilesetFilenames)
 							sequenceNode.RemoveNodes("TilesetFilenames");
 
-						if (!sequenceNode.Value.Nodes.Any())
+						if (sequenceNode.Value.Nodes.Count == 0)
 							imageNode.RemoveNode(sequenceNode);
 					}
 
@@ -328,13 +328,13 @@ namespace OpenRA.Mods.Common.UpdateRules.Rules
 						sequenceNode.RemoveNodes("TilesetFilenames");
 
 					var tilesetFilenamesNode = sequenceNode.LastChildMatching("TilesetFilenames");
-					if (allSequencesHaveTilesetFilenames && tilesetFilenamesNode != null && !tilesetFilenamesNode.Value.Nodes.Any())
+					if (allSequencesHaveTilesetFilenames && tilesetFilenamesNode != null && tilesetFilenamesNode.Value.Nodes.Count == 0)
 						sequenceNode.RemoveNode(tilesetFilenamesNode);
 				}
 			}
 
 			foreach (var sequenceNode in imageNode.Value.Nodes.ToList())
-				if (implicitInheritedSequences.Contains(sequenceNode.Key) && !sequenceNode.Value.Nodes.Any())
+				if (implicitInheritedSequences.Contains(sequenceNode.Key) && sequenceNode.Value.Nodes.Count == 0)
 					imageNode.RemoveNode(sequenceNode);
 		}
 
@@ -424,7 +424,7 @@ namespace OpenRA.Mods.Common.UpdateRules.Rules
 						if (overrideNode.Value.Value == filenameNode.Value.Value)
 							tilesetFilenamesNode.Value.Nodes.Remove(overrideNode);
 
-					if (!tilesetFilenamesNode.Value.Nodes.Any())
+					if (tilesetFilenamesNode.Value.Nodes.Count == 0)
 						sequenceNode.RemoveNode(tilesetFilenamesNode);
 
 					sequenceNode.Value.Nodes.Insert(0, filenameNode);

OpenRA.Mods.Common/UpdateRules/UpdatePath.cs

@@ -114,7 +114,7 @@ namespace OpenRA.Mods.Common.UpdateRules
 			}),
 		};
 
-		public static IEnumerable<UpdateRule> FromSource(ObjectCreator objectCreator, string source, bool chain = true)
+		public static IReadOnlyCollection<UpdateRule> FromSource(ObjectCreator objectCreator, string source, bool chain = true)
 		{
 			// Use reflection to identify types
 			var namedType = objectCreator.FindType(source);
@@ -143,12 +143,12 @@ namespace OpenRA.Mods.Common.UpdateRules
 			this.chainToSource = chainToSource;
 		}
 
-		IEnumerable<UpdateRule> Rules(bool chain = true)
+		IReadOnlyCollection<UpdateRule> Rules(bool chain = true)
 		{
 			if (chainToSource != null && chain)
 			{
 				var child = Paths.First(p => p.source == chainToSource);
-				return rules.Concat(child.Rules(chain));
+				return rules.Concat(child.Rules(chain)).ToList();
 			}
 
 			return rules;

OpenRA.Mods.Common/UtilityCommands/ExtractEmmyLuaAPI.cs

@@ -271,7 +271,7 @@ namespace OpenRA.Mods.Common.UtilityCommands
 				if (isActivity)
 					Console.WriteLine("    --- *Queued Activity*");
 
-				if (requiredTraits.Any())
+				if (requiredTraits.Length != 0)
 					Console.WriteLine($"    --- **Requires {(requiredTraits.Length == 1 ? "Trait" : "Traits")}:** {requiredTraits.Select(GetDocumentationUrl).JoinWith(", ")}");
 
 				if (memberInfo is MethodInfo methodInfo)

OpenRA.Mods.Common/UtilityCommands/UpdateMapCommand.cs

@@ -38,7 +38,7 @@ namespace OpenRA.Mods.Common.UtilityCommands
 			if (folder.OpenPackage(args[1], modData.ModFiles) is not IReadWritePackage package)
 				throw new FileNotFoundException(args[1]);
 
-			IEnumerable<UpdateRule> rules = null;
+			IReadOnlyCollection<UpdateRule> rules = null;
 			if (args.Length > 2)
 				rules = UpdatePath.FromSource(modData.ObjectCreator, args[2]);
 
@@ -77,9 +77,10 @@ namespace OpenRA.Mods.Common.UtilityCommands
 				}
 
 				var other = UpdatePath.KnownRules(modData.ObjectCreator)
-					.Where(r => !ruleGroups.Values.Any(g => g.Contains(r)));
+					.Where(r => !ruleGroups.Values.Any(g => g.Contains(r)))
+					.ToList();
 
-				if (other.Any())
+				if (other.Count != 0)
 				{
 					Console.WriteLine("      Other:");
 					foreach (var r in other)

OpenRA.Mods.Common/UtilityCommands/UpdateModCommand.cs

@@ -32,7 +32,7 @@ namespace OpenRA.Mods.Common.UtilityCommands
 			// HACK: The engine code assumes that Game.modData is set.
 			var modData = Game.ModData = utility.ModData;
 
-			IEnumerable<UpdateRule> rules = null;
+			IReadOnlyCollection<UpdateRule> rules = null;
 			if (args.Length > 1)
 				rules = UpdatePath.FromSource(modData.ObjectCreator, args[1]);
 
@@ -71,9 +71,10 @@ namespace OpenRA.Mods.Common.UtilityCommands
 				}
 
 				var other = UpdatePath.KnownRules(modData.ObjectCreator)
-					.Where(r => !ruleGroups.Values.Any(g => g.Contains(r)));
+					.Where(r => !ruleGroups.Values.Any(g => g.Contains(r)))
+					.ToList();
 
-				if (other.Any())
+				if (other.Count != 0)
 				{
 					Console.WriteLine("      Other:");
 					foreach (var r in other)
@@ -111,9 +112,9 @@ namespace OpenRA.Mods.Common.UtilityCommands
 				PrintSummary(rules, args.Contains("--detailed"));
 		}
 
-		public static void PrintSummary(IEnumerable<UpdateRule> rules, bool detailed)
+		public static void PrintSummary(IReadOnlyCollection<UpdateRule> rules, bool detailed)
 		{
-			var count = rules.Count();
+			var count = rules.Count;
 			if (count == 1)
 				Console.WriteLine("Found 1 API change:");
 			else

OpenRA.Mods.Common/Warheads/FireClusterWarhead.cs

@@ -60,9 +60,9 @@ namespace OpenRA.Mods.Common.Warheads
 
 			if (RandomClusterCount != 0)
 			{
-				var randomTargetCells = CellsMatching(targetCell, true);
+				var randomTargetCells = CellsMatching(targetCell, true).ToList();
-				var clusterCount = RandomClusterCount < 0 ? randomTargetCells.Count() : RandomClusterCount;
+				var clusterCount = RandomClusterCount < 0 ? randomTargetCells.Count : RandomClusterCount;
-				if (randomTargetCells.Any())
+				if (randomTargetCells.Count != 0)
 					for (var i = 0; i < clusterCount; i++)
 						FireProjectileAtCell(map, firedBy, target, randomTargetCells.Random(firedBy.World.SharedRandom), args);
 			}

OpenRA.Mods.Common/Widgets/Logic/EncyclopediaLogic.cs

@@ -84,7 +84,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			var actors = new List<KeyValuePair<ActorInfo, EncyclopediaInfo>>();
 			foreach (var actor in modData.DefaultRules.Actors.Values)
 			{
-				if (!actor.TraitInfos<IRenderActorPreviewSpritesInfo>().Any())
+				if (actor.TraitInfos<IRenderActorPreviewSpritesInfo>().Count == 0)
 					continue;
 
 				var statistics = actor.TraitInfoOrDefault<UpdatesPlayerStatisticsInfo>();

OpenRA.Mods.Common/Widgets/Logic/Ingame/GameInfoStatsLogic.cs

@@ -113,7 +113,8 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				.Select(p => (Player: p, PlayerStatistics: p.PlayerActor.TraitOrDefault<PlayerStatistics>()))
 				.OrderByDescending(p => p.PlayerStatistics?.Experience ?? 0)
 				.GroupBy(p => (world.LobbyInfo.ClientWithIndex(p.Player.ClientIndex) ?? new Session.Client()).Team)
-				.OrderByDescending(g => g.Sum(gg => gg.PlayerStatistics?.Experience ?? 0));
+				.OrderByDescending(g => g.Sum(gg => gg.PlayerStatistics?.Experience ?? 0))
+				.ToList();
 
 			void KickAction(Session.Client client)
 			{
@@ -133,7 +134,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 
 			foreach (var t in teams)
 			{
-				if (teams.Count() > 1)
+				if (teams.Count > 1)
 				{
 					var teamHeader = ScrollItemWidget.Setup(teamTemplate, () => false, () => { });
 					var team = t.Key > 0

OpenRA.Mods.Common/Widgets/Logic/Ingame/ObserverShroudSelectorLogic.cs

@@ -114,9 +114,10 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				.GroupBy(p => (world.LobbyInfo.ClientWithIndex(p.Player.ClientIndex) ?? new Session.Client()).Team)
 				.OrderBy(g => g.Key);
 
-			var noTeams = teams.Count() == 1;
+			var teamsList = teams.ToList();
+			var noTeams = teamsList.Count == 1;
 			var totalPlayers = 0;
-			foreach (var t in teams)
+			foreach (var t in teamsList)
 			{
 				totalPlayers += t.Count();
 				var label = noTeams ? TranslationProvider.GetString(Players) : t.Key > 0
@@ -209,12 +210,12 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				if (e.Key >= Keycode.NUMBER_0 && e.Key <= Keycode.NUMBER_9)
 				{
 					var key = (int)e.Key - (int)Keycode.NUMBER_0;
-					var team = teams.Where(t => t.Key == key).SelectMany(s => s);
+					var team = teams.Where(t => t.Key == key).SelectMany(s => s).ToList();
-					if (!team.Any())
+					if (team.Count == 0)
 						return false;
 
 					if (e.Modifiers == Modifiers.Shift)
-						team = team.Reverse();
+						team.Reverse();
 
 					selected = team.SkipWhile(t => t.Player != selected.Player).Skip(1).FirstOrDefault() ?? team.FirstOrDefault();
 					selected.OnClick();

OpenRA.Mods.Common/Widgets/Logic/Installation/InstallFromSourceLogic.cs

@@ -183,7 +183,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 						selectedPackages = availablePackages.ToDictionary(x => x.Identifier, y => y.Required);
 
 						// Ignore source if content is already installed
-						if (availablePackages.Any())
+						if (availablePackages.Length != 0)
 						{
 							Game.RunAfterTick(() =>
 							{
@@ -218,10 +218,10 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 
 				var options = new Dictionary<string, IEnumerable<string>>();
 
-				if (gameSources.Any())
+				if (gameSources.Count != 0)
 					options.Add(TranslationProvider.GetString(GameSources), gameSources);
 
-				if (digitalInstalls.Any())
+				if (digitalInstalls.Count != 0)
 					options.Add(TranslationProvider.GetString(DigitalInstalls), digitalInstalls);
 
 				Game.RunAfterTick(() =>

OpenRA.Mods.Common/Widgets/Logic/MapChooserLogic.cs

@@ -322,18 +322,19 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			if (!int.TryParse(mapFilter, out var playerCountFilter))
 				playerCountFilter = -1;
 
-			var validMaps = tabMaps[tab]
+			var maps = tabMaps[tab]
 				.Where(m => category == null || m.Categories.Contains(category))
 				.Where(m => mapFilter == null ||
 					(m.Title != null && m.Title.Contains(mapFilter, StringComparison.CurrentCultureIgnoreCase)) ||
 					(m.Author != null && m.Author.Contains(mapFilter, StringComparison.CurrentCultureIgnoreCase)) ||
 					m.PlayerCount == playerCountFilter);
 
-			IOrderedEnumerable<MapPreview> maps;
 			if (orderByFunc == null)
-				maps = validMaps.OrderBy(m => m.Title);
+				maps = maps.OrderBy(m => m.Title);
 			else
-				maps = validMaps.OrderBy(orderByFunc).ThenBy(m => m.Title);
+				maps = maps.OrderBy(orderByFunc).ThenBy(m => m.Title);
+
+			maps = maps.ToList();
 
 			scrollpanels[tab].RemoveChildren();
 			foreach (var loop in maps)

OpenRA.Mods.Common/Widgets/Logic/ReplayBrowserLogic.cs

@@ -715,10 +715,11 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 
 				var players = replay.GameInfo.Players
 					.GroupBy(p => p.Team)
-					.OrderBy(g => g.Key);
+					.OrderBy(g => g.Key)
+					.ToList();
 
 				var teams = new Dictionary<string, IEnumerable<GameInformation.Player>>();
-				var noTeams = players.Count() == 1;
+				var noTeams = players.Count == 1;
 				foreach (var p in players)
 				{
 					var label = noTeams ? TranslationProvider.GetString(Players) : p.Key > 0

OpenRA.Mods.Common/Widgets/Logic/ServerListLogic.cs

@@ -572,10 +572,11 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			var players = server.Clients
 				.Where(c => !c.IsSpectator)
 				.GroupBy(p => p.Team)
-				.OrderBy(g => g.Key);
+				.OrderBy(g => g.Key)
+				.ToList();
 
 			var teams = new Dictionary<string, IEnumerable<GameClient>>();
-			var noTeams = players.Count() == 1;
+			var noTeams = players.Count == 1;
 			foreach (var p in players)
 			{
 				var label = noTeams ? TranslationProvider.GetString(Players) : p.Key > 0

OpenRA.Mods.Common/Widgets/Logic/Settings/HotkeysSettingsLogic.cs

@@ -183,9 +183,10 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			{
 				var typesInGroup = hg.Value;
 				var keysInGroup = modData.Hotkeys.Definitions
-					.Where(hd => IsHotkeyVisibleInFilter(hd) && hd.Types.Overlaps(typesInGroup));
+					.Where(hd => IsHotkeyVisibleInFilter(hd) && hd.Types.Overlaps(typesInGroup))
+					.ToList();
 
-				if (!keysInGroup.Any())
+				if (keysInGroup.Count == 0)
 					continue;
 
 				var header = headerTemplate.Clone();

OpenRA.Mods.Common/Widgets/ObserverProductionIconsWidget.cs

@@ -102,14 +102,15 @@ namespace OpenRA.Mods.Common.Widgets
 
 			var queues = world.ActorsWithTrait<ProductionQueue>()
 				.Where(a => a.Actor.Owner == player)
-				.Select((a, i) => new { a.Trait, i });
+				.Select(a => a.Trait)
+				.ToList();
 
 			foreach (var queue in queues)
-				if (!clocks.ContainsKey(queue.Trait))
+				if (!clocks.ContainsKey(queue))
-					clocks.Add(queue.Trait, new Animation(world, ClockAnimation));
+					clocks.Add(queue, new Animation(world, ClockAnimation));
 
 			var currentItemsByItem = queues
-					.Select(a => a.Trait.CurrentItem())
+					.Select(q => q.CurrentItem())
 					.Where(pi => pi != null)
 					.GroupBy(pr => pr.Item)
 					.OrderBy(g => g.First().Queue.Info.DisplayOrder)

OpenRA.Mods.Common/Widgets/ProductionTabsWidget.cs

@@ -183,9 +183,9 @@ namespace OpenRA.Mods.Common.Widgets
 
 		public override void Draw()
 		{
-			var tabs = Groups[queueGroup].Tabs.Where(t => t.Queue.BuildableItems().Any());
+			var tabs = Groups[queueGroup].Tabs.Where(t => t.Queue.BuildableItems().Any()).ToList();
 
-			if (!tabs.Any())
+			if (tabs.Count == 0)
 				return;
 
 			var rb = RenderBounds;

OpenRA.Mods.D2k/Activities/SwallowActor.cs

@@ -51,7 +51,7 @@ namespace OpenRA.Mods.D2k.Activities
 			swallow = self.Trait<AttackSwallow>();
 		}
 
-		bool AttackTargets(Actor self, IEnumerable<Actor> targets)
+		bool AttackTargets(Actor self, IReadOnlyCollection<Actor> targets)
 		{
 			var targetLocation = target.Actor.Location;
 			foreach (var t in targets)
@@ -129,9 +129,10 @@ namespace OpenRA.Mods.D2k.Activities
 					}
 
 					var targets = self.World.ActorMap.GetActorsAt(targetLocation)
-						.Where(t => !t.Equals(self) && weapon.IsValidAgainst(t, self));
+						.Where(t => !t.Equals(self) && weapon.IsValidAgainst(t, self))
+						.ToList();
 
-					if (!targets.Any())
+					if (targets.Count == 0)
 					{
 						RevokeCondition(self);
 						return true;

OpenRA.Mods.D2k/UtilityCommands/D2kMapImporter.cs

@@ -509,17 +509,12 @@ namespace OpenRA.Mods.D2k.UtilityCommands
 
 			// HACK: The arrakis.yaml tileset file seems to be missing some tiles, so just get a replacement for them
 			// Also used for duplicate tiles that are taken from only tileset
-			if (template == null)
+			// Just get a template that contains a tile with the same ID as requested
+			template ??= terrainInfo.Templates.FirstOrDefault(t =>
 			{
-				// Just get a template that contains a tile with the same ID as requested
+				var templateInfo = (DefaultTerrainTemplateInfo)t.Value;
-				var templates = terrainInfo.Templates.Where(t =>
+				return templateInfo.Frames != null && templateInfo.Frames.Contains(tileIndex);
-				{
+			}).Value;
-					var templateInfo = (DefaultTerrainTemplateInfo)t.Value;
-					return templateInfo.Frames != null && templateInfo.Frames.Contains(tileIndex);
-				});
-				if (templates.Any())
-					template = templates.First().Value;
-			}
 
 			if (template == null)
 			{