Fix CA1851, assume_method_enumerates_parameters = true

.editorconfig

@@ -836,8 +836,8 @@ 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.linq_chain_methods = M:OpenRA.Traits.IRenderModifier.Modify*
-#dotnet_code_quality.CA1851.assume_method_enumerates_parameters = false
+dotnet_code_quality.CA1851.assume_method_enumerates_parameters = true
 dotnet_diagnostic.CA1851.severity = warning
 
 # Seal internal types.

OpenRA.Game/Exts.cs

@@ -147,7 +147,7 @@ namespace OpenRA
 
 		static T Random<T>(IEnumerable<T> ts, MersenneTwister r, bool throws)
 		{
-			var xs = ts as ICollection<T>;
+			var xs = ts as IReadOnlyCollection<T>;
 			xs ??= ts.ToList();
 			if (xs.Count == 0)
 			{

OpenRA.Game/Game.cs

@@ -523,10 +523,11 @@ namespace OpenRA
 				.Where(m => m.Status == MapStatus.Available && m.Visibility.HasFlag(MapVisibility.Shellmap))
 				.Select(m => m.Uid);
 
-			if (!shellmaps.Any())
+			var shellmap = shellmaps.RandomOrDefault(CosmeticRandom);
+			if (shellmap == null)
 				throw new InvalidDataException("No valid shellmaps available");
 
-			return shellmaps.Random(CosmeticRandom);
+			return shellmap;
 		}
 
 		public static void SwitchToExternalMod(ExternalMod mod, string[] launchArguments = null, Action onFailed = null)

OpenRA.Game/GameRules/ActorInfo.cs

@@ -130,6 +130,7 @@ namespace OpenRA
 
 			// Continue resolving traits as long as possible.
 			// Each time we resolve some traits, this means dependencies for other traits may then be possible to satisfy in the next pass.
+#pragma warning disable CA1851 // Possible multiple enumerations of 'IEnumerable' collection
 			var readyToResolve = more.ToList();
 			while (readyToResolve.Count != 0)
 			{
@@ -138,6 +139,7 @@ namespace OpenRA
 				readyToResolve.Clear();
 				readyToResolve.AddRange(more);
 			}
+#pragma warning restore CA1851
 
 			if (unresolved.Count != 0)
 			{

OpenRA.Game/Graphics/Viewport.cs

@@ -299,10 +299,13 @@ namespace OpenRA.Graphics
 
 		public void Center(IEnumerable<Actor> actors)
 		{
-			if (!actors.Any())
+			var actorsCollection = actors as IReadOnlyCollection<Actor>;
+			actorsCollection ??= actors.ToList();
+
+			if (actorsCollection.Count == 0)
 				return;
 
-			Center(actors.Select(a => a.CenterPosition).Average());
+			Center(actorsCollection.Select(a => a.CenterPosition).Average());
 		}
 
 		public void Center(WPos pos)

OpenRA.Game/SelectableExts.cs

@@ -62,10 +62,7 @@ namespace OpenRA.Traits
 
 		public static Actor WithHighestSelectionPriority(this IEnumerable<ActorBoundsPair> actors, int2 selectionPixel, Modifiers modifiers)
 		{
-			if (!actors.Any())
+			return actors.MaxByOrDefault(a => CalculateActorSelectionPriority(a.Actor.Info, a.Bounds, selectionPixel, modifiers)).Actor;
-				return null;
-
-			return actors.MaxBy(a => CalculateActorSelectionPriority(a.Actor.Info, a.Bounds, selectionPixel, modifiers)).Actor;
 		}
 
 		public static FrozenActor WithHighestSelectionPriority(this IEnumerable<FrozenActor> actors, int2 selectionPixel, Modifiers modifiers)

OpenRA.Game/Support/AssemblyLoader.cs

@@ -349,7 +349,7 @@ namespace OpenRA.Support
 			return Enumerable.Concat(new[] { runtimeGraph.Runtime }, runtimeGraph?.Fallbacks ?? Enumerable.Empty<string>());
 		}
 
-		static IEnumerable<string> SelectAssets(IEnumerable<string> rids, IEnumerable<RuntimeAssetGroup> groups)
+		static IEnumerable<string> SelectAssets(IEnumerable<string> rids, IReadOnlyCollection<RuntimeAssetGroup> groups)
 		{
 			foreach (var rid in rids)
 			{

OpenRA.Game/Traits/TraitsInterfaces.cs

@@ -455,7 +455,7 @@ namespace OpenRA.Traits
 	public interface ISelection
 	{
 		int Hash { get; }
-		IEnumerable<Actor> Actors { get; }
+		IReadOnlyCollection<Actor> Actors { get; }
 
 		void Add(Actor a);
 		void Remove(Actor a);

OpenRA.Mods.Common/Activities/Air/Land.cs

@@ -11,6 +11,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Primitives;
@@ -211,7 +212,7 @@ namespace OpenRA.Mods.Common.Activities
 
 			if (!landingInitiated)
 			{
-				var blockingCells = clearCells.Append(landingCell);
+				var blockingCells = clearCells.Append(landingCell).ToList();
 
 				if (!aircraft.CanLand(blockingCells, target.Actor))
 				{

OpenRA.Mods.Common/Lint/CheckConditions.cs

@@ -66,12 +66,12 @@ namespace OpenRA.Mods.Common.Lint
 							granted.Add(g);
 				}
 
-				var unconsumed = granted.Except(consumed);
+				var unconsumed = granted.Except(consumed).ToList();
-				if (unconsumed.Any())
+				if (unconsumed.Count != 0)
 					emitWarning($"Actor type `{actorInfo.Key}` grants conditions that are not consumed: {unconsumed.JoinWith(", ")}.");
 
-				var ungranted = consumed.Except(granted);
+				var ungranted = consumed.Except(granted).ToList();
-				if (ungranted.Any())
+				if (ungranted.Count != 0)
 					emitError($"Actor type `{actorInfo.Key}` consumes conditions that are not granted: {ungranted.JoinWith(", ")}.");
 			}
 		}

OpenRA.Mods.Common/Lint/CheckSyncAnnotations.cs

@@ -21,8 +21,7 @@ namespace OpenRA.Mods.Common.Lint
 		public void Run(Action<string> emitError, Action<string> emitWarning, ModData modData)
 		{
 			var modTypes = modData.ObjectCreator.GetTypes();
-			CheckTypesWithSyncableMembersImplementSyncInterface(modTypes, emitWarning);
+			CheckTypes(modTypes, emitWarning);
-			CheckTypesImplementingSyncInterfaceHaveSyncableMembers(modTypes, emitWarning);
 		}
 
 		static readonly Type SyncInterface = typeof(ISync);
@@ -45,18 +44,18 @@ namespace OpenRA.Mods.Common.Lint
 			return false;
 		}
 
-		static void CheckTypesWithSyncableMembersImplementSyncInterface(IEnumerable<Type> types, Action<string> emitWarning)
+		static void CheckTypes(IEnumerable<Type> types, Action<string> emitWarning)
 		{
 			foreach (var type in types)
-				if (!TypeImplementsSync(type) && AnyTypeMemberIsSynced(type))
+			{
-					emitWarning($"{type.FullName} has members with the Sync attribute but does not implement ISync.");
+				var typeImplementsSync = TypeImplementsSync(type);
-		}
+				var anyTypeMemberIsSynced = AnyTypeMemberIsSynced(type);
 
-		static void CheckTypesImplementingSyncInterfaceHaveSyncableMembers(IEnumerable<Type> types, Action<string> emitWarning)
+				if (!typeImplementsSync && anyTypeMemberIsSynced)
-		{
+					emitWarning($"{type.FullName} has members with the Sync attribute but does not implement ISync.");
-			foreach (var type in types)
+				else if (typeImplementsSync && !anyTypeMemberIsSynced)
-				if (TypeImplementsSync(type) && !AnyTypeMemberIsSynced(type))
 					emitWarning($"{type.FullName} implements ISync but does not use the Sync attribute on any members.");
+			}
 		}
 	}
 }

OpenRA.Mods.Common/Orders/UnitOrderGenerator.cs

@@ -85,7 +85,7 @@ namespace OpenRA.Mods.Common.Orders
 					return cursorOrder.Cursor;
 
 				useSelect = target.Type == TargetType.Actor && target.Actor.Info.HasTraitInfo<ISelectableInfo>() &&
-					(mi.Modifiers.HasModifier(Modifiers.Shift) || !world.Selection.Actors.Any());
+					(mi.Modifiers.HasModifier(Modifiers.Shift) || world.Selection.Actors.Count == 0);
 			}
 
 			return useSelect ? worldSelectCursor : worldDefaultCursor;

OpenRA.Mods.Common/Scripting/Global/ActorGlobal.cs

@@ -72,7 +72,8 @@ namespace OpenRA.Mods.Common.Scripting
 			}
 
 			var initializers = initType.GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance)
-				.Where(m => m.Name == "Initialize" && m.GetParameters().Length == 1);
+				.Where(m => m.Name == "Initialize" && m.GetParameters().Length == 1)
+				.ToList();
 
 			foreach (var initializer in initializers)
 			{

OpenRA.Mods.Common/ServerTraits/LobbyCommands.cs

@@ -530,9 +530,9 @@ namespace OpenRA.Mods.Common.Server
 
 					// Pick a random color for the bot
 					var colorManager = server.ModData.DefaultRules.Actors[SystemActors.World].TraitInfo<IColorPickerManagerInfo>();
-					var terrainColors = server.ModData.DefaultTerrainInfo[server.Map.TileSet].RestrictedPlayerColors;
+					var terrainColors = server.ModData.DefaultTerrainInfo[server.Map.TileSet].RestrictedPlayerColors.ToList();
 					var playerColors = server.LobbyInfo.Clients.Select(c => c.Color)
-						.Concat(server.Map.Players.Players.Values.Select(p => p.Color));
+						.Concat(server.Map.Players.Players.Values.Select(p => p.Color)).ToList();
 
 					bot.Color = bot.PreferredColor = colorManager.RandomPresetColor(server.Random, terrainColors, playerColors);
 
@@ -935,7 +935,8 @@ namespace OpenRA.Mods.Common.Server
 					return true;
 
 				var factions = server.Map.WorldActorInfo.TraitInfos<FactionInfo>()
-					.Where(f => f.Selectable).Select(f => f.InternalName);
+					.Where(f => f.Selectable).Select(f => f.InternalName)
+					.ToList();
 
 				var faction = parts[1];
 				if (!factions.Contains(faction))
@@ -1250,7 +1251,7 @@ namespace OpenRA.Mods.Common.Server
 						server.SendLocalizedMessageTo(connectionToEcho, message);
 				}
 
-				var terrainColors = server.ModData.DefaultTerrainInfo[server.Map.TileSet].RestrictedPlayerColors;
+				var terrainColors = server.ModData.DefaultTerrainInfo[server.Map.TileSet].RestrictedPlayerColors.ToList();
 				var playerColors = server.LobbyInfo.Clients.Where(c => c.Index != playerIndex).Select(c => c.Color)
 					.Concat(server.Map.Players.Players.Values.Select(p => p.Color)).ToList();
 

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

@@ -239,9 +239,10 @@ namespace OpenRA.Mods.Common.Traits
 		CPos ChooseRallyLocationNear(Actor producer)
 		{
 			var possibleRallyPoints = world.Map.FindTilesInCircle(producer.Location, Info.RallyPointScanRadius)
-				.Where(c => IsRallyPointValid(c, producer.Info.TraitInfoOrDefault<BuildingInfo>()));
+				.Where(c => IsRallyPointValid(c, producer.Info.TraitInfoOrDefault<BuildingInfo>()))
+				.ToList();
 
-			if (!possibleRallyPoints.Any())
+			if (possibleRallyPoints.Count == 0)
 			{
 				AIUtils.BotDebug("{0} has no possible rallypoint near {1}", producer.Owner, producer.Location);
 				return producer.Location;

OpenRA.Mods.Common/Traits/BotModules/BotModuleLogic/BaseBuilderQueueManager.cs

@@ -229,7 +229,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		ActorInfo ChooseBuildingToBuild(ProductionQueue queue)
 		{
-			var buildableThings = queue.BuildableItems();
+			var buildableThings = queue.BuildableItems().ToList();
 
 			// This gets used quite a bit, so let's cache it here
 			var power = GetProducibleBuilding(baseBuilder.Info.PowerTypes, buildableThings,

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

@@ -154,12 +154,13 @@ namespace OpenRA.Mods.Common.Traits
 			if (Info.CapturableActorTypes.Count > 0)
 				capturableTargetOptions = capturableTargetOptions.Where(target => Info.CapturableActorTypes.Contains(target.Info.Name.ToLowerInvariant()));
 
-			if (!capturableTargetOptions.Any())
+			var capturableTargetOptionsList = capturableTargetOptions.ToList();
+			if (capturableTargetOptionsList.Count == 0)
 				return;
 
 			foreach (var capturer in capturers)
 			{
-				var targetActor = capturableTargetOptions.MinByOrDefault(target => (target.CenterPosition - capturer.Actor.CenterPosition).LengthSquared);
+				var targetActor = capturableTargetOptionsList.MinByOrDefault(target => (target.CenterPosition - capturer.Actor.CenterPosition).LengthSquared);
 				if (targetActor == null)
 					continue;
 

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

@@ -197,7 +197,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		internal Actor FindClosestEnemy(WPos pos)
 		{
-			var units = World.Actors.Where(IsPreferredEnemyUnit);
+			var units = World.Actors.Where(IsPreferredEnemyUnit).ToList();
 			return units.Where(IsNotHiddenUnit).ClosestTo(pos) ?? units.ClosestTo(pos);
 		}
 

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

@@ -35,10 +35,9 @@ namespace OpenRA.Mods.Common.Traits.BotModules.Squads
 				&& mobile.PathFinder.PathExistsForLocomotor(mobile.Locomotor, first.Location, a.Location)
 				&& a.AppearsHostileTo(first));
 
-			if (navalProductions.Any())
+			var nearest = navalProductions.ClosestTo(first);
+			if (nearest != null)
 			{
-				var nearest = navalProductions.ClosestTo(first);
-
 				// Return nearest when it is FAR enough.
 				// If the naval production is within MaxBaseRadius, it implies that
 				// this squad is close to enemy territory and they should expect a naval combat;

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

@@ -163,11 +163,8 @@ namespace OpenRA.Mods.Common.Traits
 		ActorInfo ChooseRandomUnitToBuild(ProductionQueue queue)
 		{
 			var buildableThings = queue.BuildableItems();
-			if (!buildableThings.Any())
+			var unit = buildableThings.RandomOrDefault(world.LocalRandom);
-				return null;
+			return unit != null && HasAdequateAirUnitReloadBuildings(unit) ? unit : null;
-
-			var unit = buildableThings.Random(world.LocalRandom);
-			return HasAdequateAirUnitReloadBuildings(unit) ? unit : null;
 		}
 
 		ActorInfo ChooseUnitToBuild(ProductionQueue queue)

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

@@ -115,7 +115,7 @@ namespace OpenRA.Mods.Common.Traits
 			if (Repairers.Remove(player))
 			{
 				UpdateCondition(self);
-				if (!Repairers.Any())
+				if (Repairers.Count == 0)
 				{
 					Game.Sound.PlayNotification(self.World.Map.Rules, player, "Speech", Info.RepairingStoppedNotification, player.Faction.InternalName);
 					TextNotificationsManager.AddTransientLine(self.Owner, Info.RepairingStoppedTextNotification);

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

@@ -111,11 +111,9 @@ namespace OpenRA.Mods.Common.Traits
 
 		CPos? ChooseEmptyCellNear(Actor a, string unit)
 		{
-			var possibleCells = GetSuitableCells(a.Location, unit);
+			return GetSuitableCells(a.Location, unit)
-			if (!possibleCells.Any())
+				.Cast<CPos?>()
-				return null;
+				.RandomOrDefault(self.World.SharedRandom);
-
-			return possibleCells.Random(self.World.SharedRandom);
 		}
 	}
 }

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

@@ -82,7 +82,7 @@ namespace OpenRA.Mods.Common.Traits
 			return false;
 		}
 
-		Color MakeValid(float hue, float sat, float val, MersenneTwister random, IEnumerable<Color> terrainColors, IEnumerable<Color> playerColors, Action<string> onError)
+		Color MakeValid(float hue, float sat, float val, MersenneTwister random, IReadOnlyCollection<Color> terrainColors, IReadOnlyCollection<Color> playerColors, Action<string> onError)
 		{
 			// Clamp saturation without triggering a warning
 			// This can only happen due to rounding errors (common) or modified clients (rare)
@@ -132,7 +132,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		Color[] IColorPickerManagerInfo.PresetColors => PresetColors;
 
-		Color IColorPickerManagerInfo.RandomPresetColor(MersenneTwister random, IEnumerable<Color> terrainColors, IEnumerable<Color> playerColors)
+		Color IColorPickerManagerInfo.RandomPresetColor(MersenneTwister random, IReadOnlyCollection<Color> terrainColors, IReadOnlyCollection<Color> playerColors)
 		{
 			foreach (var color in PresetColors.Shuffle(random))
 			{
@@ -148,13 +148,13 @@ namespace OpenRA.Mods.Common.Traits
 			return MakeValid(randomHue, randomSat, randomVal, random, terrainColors, playerColors, null);
 		}
 
-		Color IColorPickerManagerInfo.MakeValid(Color color, MersenneTwister random, IEnumerable<Color> terrainColors, IEnumerable<Color> playerColors, Action<string> onError)
+		Color IColorPickerManagerInfo.MakeValid(Color color, MersenneTwister random, IReadOnlyCollection<Color> terrainColors, IReadOnlyCollection<Color> playerColors, Action<string> onError)
 		{
 			var (_, h, s, v) = color.ToAhsv();
 			return MakeValid(h, s, v, random, terrainColors, playerColors, onError);
 		}
 
-		Color IColorPickerManagerInfo.RandomValidColor(MersenneTwister random, IEnumerable<Color> terrainColors, IEnumerable<Color> playerColors)
+		Color IColorPickerManagerInfo.RandomValidColor(MersenneTwister random, IReadOnlyCollection<Color> terrainColors, IReadOnlyCollection<Color> playerColors)
 		{
 			var h = random.NextFloat();
 			var s = float2.Lerp(HsvSaturationRange[0], HsvSaturationRange[1], random.NextFloat());

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

@@ -47,7 +47,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		public void CreateControlGroup(int group)
 		{
-			if (!world.Selection.Actors.Any())
+			if (world.Selection.Actors.Count == 0)
 				return;
 
 			controlGroups[group].Clear();
@@ -59,7 +59,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		public void AddSelectionToControlGroup(int group)
 		{
-			if (!world.Selection.Actors.Any())
+			if (world.Selection.Actors.Count == 0)
 				return;
 
 			RemoveActorsFromAllControlGroups(world.Selection.Actors);

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

@@ -94,7 +94,7 @@ namespace OpenRA.Mods.Common.Traits
 			Actor ignoreActor = null,
 			bool laneBias = true)
 		{
-			return FindPathToTarget(self, sources, target, check, customCost, ignoreActor, laneBias);
+			return FindPathToTarget(self, sources.ToList(), target, check, customCost, ignoreActor, laneBias);
 		}
 
 		/// <summary>
@@ -125,11 +125,14 @@ namespace OpenRA.Mods.Common.Traits
 			// and calling the existing methods that allow multiple sources and one target.
 			// However there is a case of asymmetry we must handle, an actor may move out of a inaccessible source,
 			// but may not move onto a inaccessible target. We must account for this when performing the swap.
+			var targetsList = targets.ToList();
+			if (targetsList.Count == 0)
+				return NoPath;
 
 			// As targets must be accessible, determine accessible targets in advance so when they becomes the sources
 			// we don't accidentally allow an inaccessible position to become viable.
 			var locomotor = GetActorLocomotor(self);
-			var accessibleTargets = targets
+			var accessibleTargets = targetsList
 				.Where(target =>
 					PathSearch.CellAllowsMovement(self.World, locomotor, target, customCost)
 					&& locomotor.MovementCostToEnterCell(self, target, check, ignoreActor, true) != PathGraph.MovementCostForUnreachableCell)
@@ -146,7 +149,7 @@ namespace OpenRA.Mods.Common.Traits
 			if (sourceIsAccessible)
 			{
 				// As both ends are accessible, we can freely swap them.
-				path = FindPathToTarget(self, targets, source, check, customCost, ignoreActor, laneBias);
+				path = FindPathToTarget(self, targetsList, source, check, customCost, ignoreActor, laneBias);
 			}
 			else
 			{
@@ -167,11 +170,10 @@ namespace OpenRA.Mods.Common.Traits
 		}
 
 		List<CPos> FindPathToTarget(
-			Actor self, IEnumerable<CPos> sources, CPos target, BlockedByActor check,
+			Actor self, List<CPos> sources, CPos target, BlockedByActor check,
 			Func<CPos, int> customCost, Actor ignoreActor, bool laneBias)
 		{
-			var sourcesList = sources.ToList();
+			if (sources.Count == 0)
-			if (sourcesList.Count == 0)
 				return NoPath;
 
 			var locomotor = GetActorLocomotor(self);
@@ -183,9 +185,9 @@ namespace OpenRA.Mods.Common.Traits
 				return NoPath;
 
 			// When searching from only one source cell, some optimizations are possible.
-			if (sourcesList.Count == 1)
+			if (sources.Count == 1)
 			{
-				var source = sourcesList[0];
+				var source = sources[0];
 
 				// For adjacent cells on the same layer, we can return the path without invoking a full search.
 				if (source.Layer == target.Layer && (source - target).LengthSquared < 3)
@@ -204,7 +206,7 @@ namespace OpenRA.Mods.Common.Traits
 
 			// Use a hierarchical path search, which performs a guided unidirectional search.
 			return GetHierarchicalPathFinder(locomotor, check, ignoreActor).FindPath(
-				self, sourcesList, target, check, DefaultHeuristicWeightPercentage, customCost, ignoreActor, laneBias, pathFinderOverlay);
+				self, sources, target, check, DefaultHeuristicWeightPercentage, customCost, ignoreActor, laneBias, pathFinderOverlay);
 		}
 
 		HierarchicalPathFinder GetHierarchicalPathFinder(Locomotor locomotor, BlockedByActor check, Actor ignoreActor)

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

@@ -25,7 +25,7 @@ namespace OpenRA.Mods.Common.Traits
 	public class Selection : ISelection, INotifyCreated, INotifyOwnerChanged, ITick, IGameSaveTraitData
 	{
 		public int Hash { get; private set; }
-		public IEnumerable<Actor> Actors => actors;
+		public IReadOnlyCollection<Actor> Actors => actors;
 
 		readonly HashSet<Actor> actors = new();
 		readonly List<Actor> rolloverActors = new();
@@ -91,10 +91,13 @@ namespace OpenRA.Mods.Common.Traits
 
 		public virtual void Combine(World world, IEnumerable<Actor> newSelection, bool isCombine, bool isClick)
 		{
+			var newSelectionCollection = newSelection as IReadOnlyCollection<Actor>;
+			newSelectionCollection ??= newSelection.ToList();
+
 			if (isClick)
 			{
 				// TODO: select BEST, not FIRST
-				var adjNewSelection = newSelection.Take(1);
+				var adjNewSelection = newSelectionCollection.Take(1);
 				if (isCombine)
 					actors.SymmetricExceptWith(adjNewSelection);
 				else
@@ -106,17 +109,17 @@ namespace OpenRA.Mods.Common.Traits
 			else
 			{
 				if (isCombine)
-					actors.UnionWith(newSelection);
+					actors.UnionWith(newSelectionCollection);
 				else
 				{
 					actors.Clear();
-					actors.UnionWith(newSelection);
+					actors.UnionWith(newSelectionCollection);
 				}
 			}
 
 			UpdateHash();
 
-			foreach (var a in newSelection)
+			foreach (var a in newSelectionCollection)
 				foreach (var sel in a.TraitsImplementing<INotifySelected>())
 					sel.Selected(a);
 

OpenRA.Mods.Common/TraitsInterfaces.cs

@@ -380,9 +380,9 @@ namespace OpenRA.Mods.Common.Traits
 		(float VMin, float VMax) ValueRange { get; }
 		event Action<Color> OnColorPickerColorUpdate;
 		Color[] PresetColors { get; }
-		Color RandomPresetColor(MersenneTwister random, IEnumerable<Color> terrainColors, IEnumerable<Color> playerColors);
+		Color RandomPresetColor(MersenneTwister random, IReadOnlyCollection<Color> terrainColors, IReadOnlyCollection<Color> playerColors);
-		Color RandomValidColor(MersenneTwister random, IEnumerable<Color> terrainColors, IEnumerable<Color> playerColors);
+		Color RandomValidColor(MersenneTwister random, IReadOnlyCollection<Color> terrainColors, IReadOnlyCollection<Color> playerColors);
-		Color MakeValid(Color color, MersenneTwister random, IEnumerable<Color> terrainColors, IEnumerable<Color> playerColors, Action<string> onError = null);
+		Color MakeValid(Color color, MersenneTwister random, IReadOnlyCollection<Color> terrainColors, IReadOnlyCollection<Color> playerColors, Action<string> onError = null);
 		void ShowColorDropDown(DropDownButtonWidget dropdownButton, Color initialColor, string initialFaction, WorldRenderer worldRenderer, Action<Color> onExit);
 	}
 

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

@@ -57,7 +57,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 					.SelectMany(t => t.Value.RestrictedPlayerColors)
 					.Distinct()
 					.ToList();
-				var playerColors = Enumerable.Empty<Color>();
+				var playerColors = Array.Empty<Color>();
 				randomButton.OnClick = () =>
 				{
 					var randomColor = colorManager.RandomValidColor(world.LocalRandom, terrainColors, playerColors);
@@ -140,7 +140,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 					var colorIndex = j * paletteCols + i;
 
 					var newSwatch = (ColorBlockWidget)customColorTemplate.Clone();
-					var getColor = new CachedTransform<Color, Color>(c => colorManager.MakeValid(c, world.LocalRandom, Enumerable.Empty<Color>(), Enumerable.Empty<Color>()));
+					var getColor = new CachedTransform<Color, Color>(c => colorManager.MakeValid(c, world.LocalRandom, Array.Empty<Color>(), Array.Empty<Color>()));
 
 					newSwatch.GetColor = () => getColor.Update(Game.Settings.Player.CustomColors[colorIndex]);
 					newSwatch.IsVisible = () => Game.Settings.Player.CustomColors.Length > colorIndex;

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

@@ -79,7 +79,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			};
 		}
 
-		IEnumerable<KeyValuePair<ActorInfo, EncyclopediaInfo>> GetFilteredActorEncyclopediaPairs()
+		IReadOnlyCollection<KeyValuePair<ActorInfo, EncyclopediaInfo>> GetFilteredActorEncyclopediaPairs()
 		{
 			var actors = new List<KeyValuePair<ActorInfo, EncyclopediaInfo>>();
 			foreach (var actor in modData.DefaultRules.Actors.Values)
@@ -149,9 +149,11 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			var buildable = actor.TraitInfoOrDefault<BuildableInfo>();
 			if (buildable != null)
 			{
-				var prerequisites = buildable.Prerequisites.Select(a => ActorName(modData.DefaultRules, a))
+				var prerequisites = buildable.Prerequisites
-					.Where(s => !s.StartsWith('~') && !s.StartsWith('!'));
+					.Select(a => ActorName(modData.DefaultRules, a))
-				if (prerequisites.Any())
+					.Where(s => !s.StartsWith('~') && !s.StartsWith('!'))
+					.ToList();
+				if (prerequisites.Count != 0)
 					text += $"Requires {prerequisites.JoinWith(", ")}\n\n";
 			}
 

OpenRA.Mods.Common/Widgets/Logic/Ingame/Hotkeys/SelectAllUnitsHotkeyLogic.cs

@@ -53,7 +53,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic.Ingame
 			var newSelection = SelectionUtils.SelectActorsOnScreen(world, worldRenderer, null, eligiblePlayers).SubsetWithHighestSelectionPriority(e.Modifiers).ToList();
 
 			// Check if selecting actors on the screen has selected new units
-			if (newSelection.Count > selection.Actors.Count())
+			if (newSelection.Count > selection.Actors.Count)
 				TextNotificationsManager.AddFeedbackLine(SelectedUnitsAcrossScreen, Translation.Arguments("units", newSelection.Count));
 			else
 			{

OpenRA.Mods.Common/Widgets/Logic/Ingame/Hotkeys/SelectUnitsByTypeHotkeyLogic.cs

@@ -52,7 +52,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic.Ingame
 			if (world.IsGameOver)
 				return false;
 
-			if (!selection.Actors.Any())
+			if (selection.Actors.Count == 0)
 			{
 				TextNotificationsManager.AddFeedbackLine(NothingSelected);
 				Game.Sound.PlayNotification(world.Map.Rules, world.LocalPlayer, "Sounds", ClickDisabledSound, null);
@@ -78,7 +78,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic.Ingame
 			var newSelection = SelectionUtils.SelectActorsOnScreen(world, worldRenderer, selectedClasses, eligiblePlayers).ToList();
 
 			// Check if selecting actors on the screen has selected new units
-			if (newSelection.Count > selection.Actors.Count())
+			if (newSelection.Count > selection.Actors.Count)
 				TextNotificationsManager.AddFeedbackLine(SelectedUnitsAcrossScreen, Translation.Arguments("units", newSelection.Count));
 			else
 			{

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

@@ -112,9 +112,9 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				requiredWidget.IsVisible = () => p.Value.Required;
 
 				var sourceWidget = container.Get<ImageWidget>("SOURCE");
-				var sourceTitles = p.Value.Sources.Select(s => sources[s].Title).Distinct();
+				var sourceTitles = p.Value.Sources.Select(s => sources[s].Title).Distinct().ToList();
 				var sourceList = sourceTitles.JoinWith("\n");
-				var isSourceAvailable = sourceTitles.Any();
+				var isSourceAvailable = sourceTitles.Count != 0;
 				sourceWidget.GetTooltipText = () => sourceList;
 				sourceWidget.IsVisible = () => isSourceAvailable;
 

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

@@ -136,9 +136,10 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 						})
 						.Where(x => x.Index != -1)
 						.OrderBy(x => x.Index)
-						.Select(x => x.Preview);
+						.Select(x => x.Preview)
+						.ToList();
 
-					if (previews.Any())
+					if (previews.Count != 0)
 					{
 						CreateMissionGroup(kv.Key, previews, onExit);
 						allPreviews.AddRange(previews);
@@ -148,9 +149,12 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 
 			// Add an additional group for loose missions
 			var loosePreviews = modData.MapCache
-				.Where(p => p.Status == MapStatus.Available && p.Visibility.HasFlag(MapVisibility.MissionSelector) && !allPreviews.Any(a => a.Uid == p.Uid));
+				.Where(p => p.Status == MapStatus.Available &&
+					p.Visibility.HasFlag(MapVisibility.MissionSelector) &&
+					!allPreviews.Any(a => a.Uid == p.Uid))
+				.ToList();
 
-			if (loosePreviews.Any())
+			if (loosePreviews.Count != 0)
 			{
 				CreateMissionGroup("Missions", loosePreviews, onExit);
 				allPreviews.AddRange(loosePreviews);

OpenRA.Mods.Common/Widgets/ProductionPaletteWidget.cs

@@ -443,7 +443,7 @@ namespace OpenRA.Mods.Common.Widgets
 			if (facility == null || facility.OccupiesSpace == null)
 				return true;
 
-			if (selection.Actors.Count() == 1 && selection.Contains(facility))
+			if (selection.Actors.Count == 1 && selection.Contains(facility))
 				viewport.Center(selection.Actors);
 			else
 				selection.Combine(World, new[] { facility }, false, true);

OpenRA.Mods.Common/Widgets/WorldInteractionControllerWidget.cs

@@ -109,7 +109,7 @@ namespace OpenRA.Mods.Common.Widgets
 			{
 				if (useClassicMouseStyle && HasMouseFocus)
 				{
-					if (!IsValidDragbox && World.Selection.Actors.Any() && !multiClick && uog.InputOverridesSelection(World, mousePos, mi))
+					if (!IsValidDragbox && World.Selection.Actors.Count != 0 && !multiClick && uog.InputOverridesSelection(World, mousePos, mi))
 					{
 						// Order units instead of selecting
 						ApplyOrders(World, mi);

OpenRA.Mods.D2k/Traits/SpiceBloom.cs

@@ -120,7 +120,7 @@ namespace OpenRA.Mods.D2k.Traits
 			if (pieces < info.Pieces[0])
 				pieces = info.Pieces[0];
 
-			var cells = self.World.Map.FindTilesInAnnulus(self.Location, 1, info.Range);
+			var cells = self.World.Map.FindTilesInAnnulus(self.Location, 1, info.Range).ToList();
 
 			for (var i = 0; i < pieces; i++)
 			{

OpenRA.Test/OpenRA.Game/PriorityQueueTest.cs

@@ -53,7 +53,7 @@ namespace OpenRA.Test
 		public void PriorityQueueAddThenRemoveTest(int count, int seed)
 		{
 			var mt = new MersenneTwister(seed);
-			var values = Enumerable.Range(0, count);
+			var values = Enumerable.Range(0, count).ToList();
 			var shuffledValues = values.Shuffle(mt).ToArray();
 
 			var queue = new Primitives.PriorityQueue<int, Int32Comparer>(default);