diff --git a/.editorconfig b/.editorconfig
index 435455fe31..044b1a1115 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -892,9 +892,15 @@ dotnet_diagnostic.CA2247.severity = warning
 # Provide correct enum argument to Enum.HasFlag.
 dotnet_diagnostic.CA2248.severity = warning
 
+# Consider using String.Contains instead of String.IndexOf.
+dotnet_diagnostic.CA2249.severity = warning
+
 # Use ThrowIfCancellationRequested.
 dotnet_diagnostic.CA2250.severity = warning
 
+# Use String.Equals over String.Compare.
+dotnet_diagnostic.CA2251.severity = warning
+
 # Ensure ThreadStatic is only used with static fields.
 dotnet_diagnostic.CA2259.severity = warning
 
diff --git a/OpenRA.Game/GameRules/ActorInfo.cs b/OpenRA.Game/GameRules/ActorInfo.cs
index a064db6ffa..035549ad5d 100644
--- a/OpenRA.Game/GameRules/ActorInfo.cs
+++ b/OpenRA.Game/GameRules/ActorInfo.cs
@@ -22,7 +22,7 @@ namespace OpenRA
 	/// </summary>
 	public class ActorInfo
 	{
-		public const string AbstractActorPrefix = "^";
+		public const char AbstractActorPrefix = '^';
 		public const char TraitInstanceSeparator = '@';
 
 		/// <summary>
diff --git a/OpenRA.Game/GameRules/Ruleset.cs b/OpenRA.Game/GameRules/Ruleset.cs
index 312c6805aa..0c6f938900 100644
--- a/OpenRA.Game/GameRules/Ruleset.cs
+++ b/OpenRA.Game/GameRules/Ruleset.cs
@@ -124,7 +124,7 @@ namespace OpenRA
 			{
 				var actors = MergeOrDefault("Manifest,Rules", fs, m.Rules, null, null,
 					k => new ActorInfo(modData.ObjectCreator, k.Key.ToLowerInvariant(), k.Value),
-					filterNode: n => n.Key.StartsWith(ActorInfo.AbstractActorPrefix, StringComparison.Ordinal));
+					filterNode: n => n.Key.StartsWith(ActorInfo.AbstractActorPrefix));
 
 				var weapons = MergeOrDefault("Manifest,Weapons", fs, m.Weapons, null, null,
 					k => new WeaponInfo(k.Value));
@@ -182,7 +182,7 @@ namespace OpenRA
 			{
 				var actors = MergeOrDefault("Rules", fileSystem, m.Rules, mapRules, dr.Actors,
 					k => new ActorInfo(modData.ObjectCreator, k.Key.ToLowerInvariant(), k.Value),
-					filterNode: n => n.Key.StartsWith(ActorInfo.AbstractActorPrefix, StringComparison.Ordinal));
+					filterNode: n => n.Key.StartsWith(ActorInfo.AbstractActorPrefix));
 
 				var weapons = MergeOrDefault("Weapons", fileSystem, m.Weapons, mapWeapons, dr.Weapons,
 					k => new WeaponInfo(k.Value));
diff --git a/OpenRA.Mods.Common/Widgets/Logic/Editor/ActorEditLogic.cs b/OpenRA.Mods.Common/Widgets/Logic/Editor/ActorEditLogic.cs
index 14d40b9716..c22bc2c9e2 100644
--- a/OpenRA.Mods.Common/Widgets/Logic/Editor/ActorEditLogic.cs
+++ b/OpenRA.Mods.Common/Widgets/Logic/Editor/ActorEditLogic.cs
@@ -491,7 +491,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 
 		public void Do()
 		{
-			actor = editorActorLayer[actorId.ToLowerInvariant()];
+			actor = editorActorLayer[actorId];
 			foreach (var editorActionHandle in handles)
 				editorActionHandle.Do(actor);
 		}
diff --git a/OpenRA.Mods.Common/Widgets/Logic/Editor/ActorSelectorLogic.cs b/OpenRA.Mods.Common/Widgets/Logic/Editor/ActorSelectorLogic.cs
index f89ace6fdc..5e945aeac4 100644
--- a/OpenRA.Mods.Common/Widgets/Logic/Editor/ActorSelectorLogic.cs
+++ b/OpenRA.Mods.Common/Widgets/Logic/Editor/ActorSelectorLogic.cs
@@ -141,7 +141,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				if (!string.IsNullOrEmpty(searchFilter))
 					FilteredCategories.AddRange(
 						allActors.Where(t => t.SearchTerms.Any(
-							s => s.IndexOf(searchFilter, StringComparison.OrdinalIgnoreCase) >= 0))
+							s => s.Contains(searchFilter, StringComparison.CurrentCultureIgnoreCase)))
 						.SelectMany(t => t.Categories)
 						.Distinct()
 						.OrderBy(x => x));
@@ -181,7 +181,8 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				if (!SelectedCategories.Overlaps(a.Categories))
 					continue;
 
-				if (!string.IsNullOrEmpty(searchFilter) && !a.SearchTerms.Any(s => s.IndexOf(searchFilter, StringComparison.OrdinalIgnoreCase) >= 0))
+				if (!string.IsNullOrEmpty(searchFilter) &&
+					!a.SearchTerms.Any(s => s.Contains(searchFilter, StringComparison.CurrentCultureIgnoreCase)))
 					continue;
 
 				var actor = a.Actor;
diff --git a/OpenRA.Mods.Common/Widgets/Logic/Editor/TileSelectorLogic.cs b/OpenRA.Mods.Common/Widgets/Logic/Editor/TileSelectorLogic.cs
index 1601b952b3..440510b54f 100644
--- a/OpenRA.Mods.Common/Widgets/Logic/Editor/TileSelectorLogic.cs
+++ b/OpenRA.Mods.Common/Widgets/Logic/Editor/TileSelectorLogic.cs
@@ -102,7 +102,8 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				if (!SelectedCategories.Overlaps(t.Categories))
 					continue;
 
-				if (!string.IsNullOrEmpty(searchFilter) && !t.SearchTerms.Any(s => s.IndexOf(searchFilter, StringComparison.OrdinalIgnoreCase) >= 0))
+				if (!string.IsNullOrEmpty(searchFilter) &&
+					!t.SearchTerms.Any(s => s.Contains(searchFilter, StringComparison.CurrentCultureIgnoreCase)))
 					continue;
 
 				var tileId = t.Template.Id;
diff --git a/OpenRA.Mods.Common/Widgets/Logic/MapChooserLogic.cs b/OpenRA.Mods.Common/Widgets/Logic/MapChooserLogic.cs
index ed2d2b77b9..73c14c5555 100644
--- a/OpenRA.Mods.Common/Widgets/Logic/MapChooserLogic.cs
+++ b/OpenRA.Mods.Common/Widgets/Logic/MapChooserLogic.cs
@@ -325,8 +325,8 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			var validMaps = tabMaps[tab]
 				.Where(m => category == null || m.Categories.Contains(category))
 				.Where(m => mapFilter == null ||
-					(m.Title != null && m.Title.IndexOf(mapFilter, StringComparison.OrdinalIgnoreCase) >= 0) ||
-					(m.Author != null && m.Author.IndexOf(mapFilter, StringComparison.OrdinalIgnoreCase) >= 0) ||
+					(m.Title != null && m.Title.Contains(mapFilter, StringComparison.CurrentCultureIgnoreCase)) ||
+					(m.Author != null && m.Author.Contains(mapFilter, StringComparison.CurrentCultureIgnoreCase)) ||
 					m.PlayerCount == playerCountFilter);
 
 			IOrderedEnumerable<MapPreview> maps;
diff --git a/OpenRA.Mods.Common/Widgets/Logic/Settings/HotkeysSettingsLogic.cs b/OpenRA.Mods.Common/Widgets/Logic/Settings/HotkeysSettingsLogic.cs
index b364cbf041..5848cdd99d 100644
--- a/OpenRA.Mods.Common/Widgets/Logic/Settings/HotkeysSettingsLogic.cs
+++ b/OpenRA.Mods.Common/Widgets/Logic/Settings/HotkeysSettingsLogic.cs
@@ -322,7 +322,8 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 		bool IsHotkeyVisibleInFilter(HotkeyDefinition hd)
 		{
 			var filter = filterInput.Text;
-			var isFilteredByName = string.IsNullOrWhiteSpace(filter) || hd.Description.Contains(filter, StringComparison.OrdinalIgnoreCase);
+			var isFilteredByName = string.IsNullOrWhiteSpace(filter) ||
+				hd.Description.Contains(filter, StringComparison.CurrentCultureIgnoreCase);
 			var isFilteredByContext = currentContext == "Any" || hd.Contexts.Contains(currentContext);
 
 			return isFilteredByName && isFilteredByContext;