Enable Net 7 and Net 8 style rules.

.editorconfig

@@ -748,7 +748,7 @@ dotnet_diagnostic.CA1305.severity = warning
 dotnet_diagnostic.CA1310.severity = warning
 
 # Specify a culture or use an invariant version.
-dotnet_diagnostic.CA1311.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1311.severity = warning
 
 ### Portability and Interoperability Rules
 ### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/interoperability-warnings
@@ -763,19 +763,19 @@ dotnet_diagnostic.CA1417.severity = warning
 dotnet_diagnostic.CA1507.severity = warning
 
 # Use ArgumentNullException throw helper.
-dotnet_diagnostic.CA1510.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1510.severity = warning
 
 # Use ArgumentException throw helper.
-dotnet_diagnostic.CA1511.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1511.severity = warning
 
 # Use ArgumentOutOfRangeException throw helper.
-dotnet_diagnostic.CA1512.severity = suggestion # TODO: Change to warning once using .NET 8 or later.
+dotnet_diagnostic.CA1512.severity = warning
 
 # Use ObjectDisposedException throw helper.
-dotnet_diagnostic.CA1513.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1513.severity = warning
 
 # Avoid redundant length argument.
-dotnet_diagnostic.CA1514.severity = suggestion # TODO: Change to warning once using .NET 8 or later.
+dotnet_diagnostic.CA1514.severity = warning
 
 ### Naming Rules
 ### https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/naming-warnings
@@ -868,8 +868,8 @@ dotnet_diagnostic.CA1843.severity = warning
 # Provide memory-based overrides of async methods when subclassing 'Stream'.
 dotnet_diagnostic.CA1844.severity = warning
 
-# Use span-based 'string.Concat'. (Not available on mono)
-dotnet_diagnostic.CA1845.severity = none
+# Use span-based 'string.Concat'.
+dotnet_diagnostic.CA1845.severity = warning
 
 # Prefer AsSpan over Substring.
 dotnet_diagnostic.CA1846.severity = warning
@@ -878,34 +878,34 @@ dotnet_diagnostic.CA1846.severity = warning
 dotnet_diagnostic.CA1847.severity = warning
 
 # Call async methods when in an async method.
-dotnet_diagnostic.CA1849.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1849.severity = warning
 
-# Prefer static HashData method over ComputeHash. (Not available on mono)
-dotnet_diagnostic.CA1850.severity = none # TODO: Change to warning once using .NET 7 or later AND once supported by mono.
+# Prefer static HashData method over ComputeHash.
+dotnet_diagnostic.CA1850.severity = warning
 
 # Possible multiple enumerations of IEnumerable collection.
 #dotnet_code_quality.CA1851.enumeration_methods =
 dotnet_code_quality.CA1851.linq_chain_methods = M:OpenRA.Traits.IRenderModifier.Modify*
 dotnet_code_quality.CA1851.assume_method_enumerates_parameters = true
-dotnet_diagnostic.CA1851.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1851.severity = warning
 
 # Seal internal types.
-dotnet_diagnostic.CA1852.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1852.severity = warning
 
 # Unnecessary call to 'Dictionary.ContainsKey(key)'.
-dotnet_diagnostic.CA1853.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1853.severity = warning
 
 # Prefer the IDictionary.TryGetValue(TKey, out TValue) method.
-dotnet_diagnostic.CA1854.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1854.severity = warning
 
 # Use Span<T>.Clear() instead of Span<T>.Fill().
-dotnet_diagnostic.CA1855.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1855.severity = warning
 
 # Incorrect usage of ConstantExpected attribute.
-dotnet_diagnostic.CA1856.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1856.severity = warning
 
 # The parameter expects a constant for optimal performance.
-dotnet_diagnostic.CA1857.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1857.severity = warning
 
 # Use StartsWith instead of IndexOf.
 dotnet_diagnostic.CA1858.severity = warning
@@ -917,24 +917,24 @@ dotnet_diagnostic.CA1860.severity = warning
 dotnet_diagnostic.CA1862.severity = warning
 
 # Use 'CompositeFormat'.
-dotnet_diagnostic.CA1863.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA1863.severity = warning
 
 # Prefer the 'IDictionary.TryAdd(TKey, TValue)' method.
-dotnet_diagnostic.CA1864.severity = suggestion # TODO: Change to warning once using .NET 8 or later.
+dotnet_diagnostic.CA1864.severity = warning
 
 # Use 'string.Method(char)' instead of 'string.Method(string)' for string with single char.
-dotnet_diagnostic.CA1865.severity = suggestion # TODO: Change to warning once using .NET 8 or later.
-dotnet_diagnostic.CA1866.severity = suggestion # TODO: Change to warning once using .NET 8 or later.
-dotnet_diagnostic.CA1867.severity = suggestion # TODO: Change to warning once using .NET 8 or later.
+dotnet_diagnostic.CA1865.severity = warning
+dotnet_diagnostic.CA1866.severity = warning
+dotnet_diagnostic.CA1867.severity = warning
 
 # Unnecessary call to 'Contains' for sets.
-dotnet_diagnostic.CA1868.severity = suggestion # TODO: Change to warning once using .NET 8 or later.
+dotnet_diagnostic.CA1868.severity = warning
 
 # Cache and reuse 'JsonSerializerOptions' instances.
-dotnet_diagnostic.CA1869.severity = suggestion # TODO: Change to warning once using .NET 8 or later.
+dotnet_diagnostic.CA1869.severity = warning
 
 # Use a cached 'SearchValues' instance.
-dotnet_diagnostic.CA1870.severity = suggestion # TODO: Change to warning once using .NET 8 or later.
+dotnet_diagnostic.CA1870.severity = warning
 
 # Do not pass a nullable struct to 'ArgumentNullException.ThrowIfNull'.
 dotnet_diagnostic.CA1871.severity = warning
@@ -964,7 +964,7 @@ dotnet_diagnostic.CA2016.severity = warning
 dotnet_diagnostic.CA2018.severity = warning
 
 # ThreadStatic fields should not use inline initialization.
-dotnet_diagnostic.CA2019.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA2019.severity = warning
 
 # Don't call Enumerable.Cast<T> or Enumerable.OfType<T> with incompatible types.
 dotnet_diagnostic.CA2021.severity = warning
@@ -1041,10 +1041,10 @@ dotnet_diagnostic.CA2250.severity = warning
 dotnet_diagnostic.CA2251.severity = warning
 
 # Ensure ThreadStatic is only used with static fields.
-dotnet_diagnostic.CA2259.severity = suggestion # TODO: Change to warning once using .NET 7 or later.
+dotnet_diagnostic.CA2259.severity = warning
 
 # Prefer generic overload when type is known.
-dotnet_diagnostic.CA2263.severity = none # TODO: Change to warning once mono is dropped.
+dotnet_diagnostic.CA2263.severity = warning
 
 # Do not pass a non-nullable value to 'ArgumentNullException.ThrowIfNull'.
 dotnet_diagnostic.CA2264.severity = warning

OpenRA.Game/CryptoUtil.cs

@@ -210,8 +210,7 @@ namespace OpenRA
 				using (var rsa = new RSACryptoServiceProvider())
 				{
 					rsa.ImportParameters(parameters);
-					using (var csp = SHA1.Create())
-						return Convert.ToBase64String(rsa.SignHash(csp.ComputeHash(data), CryptoConfig.MapNameToOID("SHA1")));
+					return Convert.ToBase64String(rsa.SignHash(SHA1.HashData(data), CryptoConfig.MapNameToOID("SHA1")));
 				}
 			}
 			catch (Exception e)
@@ -236,8 +235,7 @@ namespace OpenRA
 				using (var rsa = new RSACryptoServiceProvider())
 				{
 					rsa.ImportParameters(parameters);
-					using (var csp = SHA1.Create())
-						return rsa.VerifyHash(csp.ComputeHash(data), CryptoConfig.MapNameToOID("SHA1"), Convert.FromBase64String(signature));
+					return rsa.VerifyHash(SHA1.HashData(data), CryptoConfig.MapNameToOID("SHA1"), Convert.FromBase64String(signature));
 				}
 			}
 			catch (Exception e)
@@ -252,14 +250,12 @@ namespace OpenRA
 
 		public static string SHA1Hash(Stream data)
 		{
-			using var csp = SHA1.Create();
-			return ToHex(csp.ComputeHash(data), true);
+			return ToHex(SHA1.HashData(data), true);
 		}
 
 		public static string SHA1Hash(byte[] data)
 		{
-			using var csp = SHA1.Create();
-			return ToHex(csp.ComputeHash(data), true);
+			return ToHex(SHA1.HashData(data), true);
 		}
 
 		public static string SHA1Hash(string data)

OpenRA.Game/FileFormats/ReplayMetadata.cs

@@ -27,8 +27,7 @@ namespace OpenRA.FileFormats
 
 		public ReplayMetadata(GameInformation info)
 		{
-			if (info == null)
-				throw new ArgumentNullException(nameof(info));
+			ArgumentNullException.ThrowIfNull(info);
 
 			GameInfo = info;
 		}

OpenRA.Game/FluentBundle.cs

@@ -111,8 +111,7 @@ namespace OpenRA
 
 		public bool TryGetMessage(string key, out string value, object[] args = null)
 		{
-			if (key == null)
-				throw new ArgumentNullException(nameof(key));
+			ArgumentNullException.ThrowIfNull(key);
 
 			try
 			{

OpenRA.Game/GameInformation.cs

@@ -100,11 +100,9 @@ namespace OpenRA
 		/// <summary>Adds the player information at start-up.</summary>
 		public void AddPlayer(OpenRA.Player runtimePlayer, Session lobbyInfo)
 		{
-			if (runtimePlayer == null)
-				throw new ArgumentNullException(nameof(runtimePlayer));
+			ArgumentNullException.ThrowIfNull(runtimePlayer);
 
-			if (lobbyInfo == null)
-				throw new ArgumentNullException(nameof(lobbyInfo));
+			ArgumentNullException.ThrowIfNull(lobbyInfo);
 
 			// We don't care about spectators and map players
 			if (runtimePlayer.NonCombatant || !runtimePlayer.Playable)

OpenRA.Game/Graphics/Model.cs

@@ -31,9 +31,9 @@ namespace OpenRA.Graphics
 
 	public interface IModelWidget
 	{
-		public string Palette { get; }
-		public float Scale { get; }
-		public void Setup(Func<bool> isVisible, Func<string> getPalette, Func<string> getPlayerPalette,
+		string Palette { get; }
+		float Scale { get; }
+		void Setup(Func<bool> isVisible, Func<string> getPalette, Func<string> getPlayerPalette,
 			Func<float> getScale, Func<IModel> getVoxel, Func<WRot> getRotation);
 	}
 

OpenRA.Game/Primitives/ActionQueue.cs

@@ -23,8 +23,7 @@ namespace OpenRA.Primitives
 
 		public void Add(Action a, long desiredTime)
 		{
-			if (a == null)
-				throw new ArgumentNullException(nameof(a));
+			ArgumentNullException.ThrowIfNull(a);
 
 			lock (actions)
 			{

OpenRA.Game/Primitives/ActorInfoDictionary.cs

@@ -21,8 +21,7 @@ namespace OpenRA
 
 		public ActorInfoDictionary(IReadOnlyDictionary<string, ActorInfo> dict)
 		{
-			if (dict == null)
-				throw new ArgumentNullException(nameof(dict));
+			ArgumentNullException.ThrowIfNull(dict);
 
 			this.dict = new Dictionary<string, ActorInfo>(dict);
 		}

OpenRA.Game/Primitives/Cache.cs

@@ -21,8 +21,7 @@ namespace OpenRA.Primitives
 
 		public Cache(Func<T, U> loader, IEqualityComparer<T> c)
 		{
-			if (loader == null)
-				throw new ArgumentNullException(nameof(loader));
+			ArgumentNullException.ThrowIfNull(loader);
 
 			this.loader = loader;
 			cache = new Dictionary<T, U>(c);

OpenRA.Game/Primitives/ConcurrentCache.cs

@@ -22,8 +22,7 @@ namespace OpenRA.Primitives
 
 		public ConcurrentCache(Func<T, U> loader, IEqualityComparer<T> c)
 		{
-			if (loader == null)
-				throw new ArgumentNullException(nameof(loader));
+			ArgumentNullException.ThrowIfNull(loader);
 
 			this.loader = loader;
 			cache = new ConcurrentDictionary<T, U>(c);

OpenRA.Game/Primitives/ReadOnlyAdapterStream.cs

@@ -27,8 +27,7 @@ namespace OpenRA.Primitives
 
 		protected ReadOnlyAdapterStream(Stream stream)
 		{
-			if (stream == null)
-				throw new ArgumentNullException(nameof(stream));
+			ArgumentNullException.ThrowIfNull(stream);
 			if (!stream.CanRead)
 				throw new ArgumentException("stream must be readable.", nameof(stream));
 

OpenRA.Game/Primitives/RingBuffer.cs

@@ -65,8 +65,7 @@ namespace OpenRA.Primitives
 
 		public void CopyTo(T[] array, int arrayIndex)
 		{
-			if (array == null)
-				throw new ArgumentNullException(nameof(array));
+			ArgumentNullException.ThrowIfNull(array);
 
 			if (arrayIndex < 0)
 				throw new ArgumentNullException(nameof(arrayIndex));

OpenRA.Game/Primitives/SegmentStream.cs

@@ -32,8 +32,7 @@ namespace OpenRA.Primitives
 		/// <param name="count">The length of the segment.</param>
 		public SegmentStream(Stream stream, long offset, long count)
 		{
-			if (stream == null)
-				throw new ArgumentNullException(nameof(stream));
+			ArgumentNullException.ThrowIfNull(stream);
 			if (!stream.CanSeek)
 				throw new ArgumentException("stream must be seekable.", nameof(stream));
 			if (offset < 0)

OpenRA.Game/Scripting/ScriptMemberWrapper.cs

@@ -150,7 +150,7 @@ namespace OpenRA.Scripting
 			// Remove the namespace and the trailing "Info"
 			return types.SelectMany(i => i.GetGenericArguments())
 				.Select(g => g.Name.Split('.', StringSplitOptions.RemoveEmptyEntries).LastOrDefault())
-				.Select(s => s.EndsWith("Info", StringComparison.Ordinal) ? s.Remove(s.Length - 4, 4) : s)
+				.Select(s => s.EndsWith("Info", StringComparison.Ordinal) ? s[..^4] : s)
 				.ToArray();
 		}
 	}

OpenRA.Game/Sound/Sound.cs

@@ -359,8 +359,7 @@ namespace OpenRA
 		public bool PlayPredefined(SoundType soundType, Ruleset ruleset, Player player, Actor voicedActor, string type, string definition, string variant,
 			bool relative, WPos pos, float volumeModifier, bool attenuateVolume)
 		{
-			if (ruleset == null)
-				throw new ArgumentNullException(nameof(ruleset));
+			ArgumentNullException.ThrowIfNull(ruleset);
 
 			if (definition == null || DisableAllSounds || (DisableWorldSounds && soundType == SoundType.World))
 				return false;
@@ -460,8 +459,7 @@ namespace OpenRA
 
 		public bool PlayNotification(Ruleset rules, Player player, string type, string notification, string variant)
 		{
-			if (rules == null)
-				throw new ArgumentNullException(nameof(rules));
+			ArgumentNullException.ThrowIfNull(rules);
 
 			if (type == null || notification == null)
 				return false;

OpenRA.Mods.Cnc/SpriteLoaders/ShpTDLoader.cs

@@ -75,7 +75,7 @@ namespace OpenRA.Mods.Cnc.SpriteLoaders
 	{
 		enum Format : ushort { XORPrev = 0x20, XORLCW = 0x40, LCW = 0x80 }
 
-		class TrimmedFrame : ISpriteFrame
+		sealed class TrimmedFrame : ISpriteFrame
 		{
 			public SpriteFrameType Type => SpriteFrameType.Indexed8;
 			public Size Size { get; }

OpenRA.Mods.Common/EditorBrushes/EditorMarkerLayerBrush.cs

@@ -96,7 +96,7 @@ namespace OpenRA.Mods.Common.Widgets
 		}
 	}
 
-	class PaintMarkerTileEditorAction : IEditorAction
+	sealed class PaintMarkerTileEditorAction : IEditorAction
 	{
 		[FluentReference("amount", "type")]
 		const string AddedMarkerTiles = "notification-added-marker-tiles";
@@ -156,7 +156,7 @@ namespace OpenRA.Mods.Common.Widgets
 		}
 	}
 
-	class ClearSelectedMarkerTilesEditorAction : IEditorAction
+	sealed class ClearSelectedMarkerTilesEditorAction : IEditorAction
 	{
 		[FluentReference("amount", "type")]
 		const string ClearedSelectedMarkerTiles = "notification-cleared-selected-marker-tiles";
@@ -195,7 +195,7 @@ namespace OpenRA.Mods.Common.Widgets
 		}
 	}
 
-	class ClearAllMarkerTilesEditorAction : IEditorAction
+	sealed class ClearAllMarkerTilesEditorAction : IEditorAction
 	{
 		[FluentReference("amount")]
 		const string ClearedAllMarkerTiles = "notification-cleared-all-marker-tiles";
@@ -211,7 +211,7 @@ namespace OpenRA.Mods.Common.Widgets
 			this.markerLayerOverlay = markerLayerOverlay;
 			tiles = new Dictionary<int, HashSet<CPos>>(markerLayerOverlay.Tiles);
 
-			var allTilesCount = tiles.Values.Select(x => x.Count).Sum();
+			var allTilesCount = tiles.Values.Sum(x => x.Count);
 
 			Text = FluentProvider.GetMessage(ClearedAllMarkerTiles, "amount", allTilesCount);
 		}

OpenRA.Mods.Common/FileFormats/WavReader.cs

@@ -58,7 +58,7 @@ namespace OpenRA.Mods.Common.FileFormats
 						var audioFormat = s.ReadInt16();
 						audioType = (WaveType)audioFormat;
 
-						if (!Enum.IsDefined(typeof(WaveType), audioType))
+						if (!Enum.IsDefined(audioType))
 							throw new NotSupportedException($"Compression type {audioFormat} is not supported.");
 
 						channels = s.ReadInt16();

OpenRA.Mods.Common/FileSystem/DefaultFileSystemLoader.cs

@@ -17,7 +17,7 @@ namespace OpenRA.Mods.Common.FileSystem
 	[RequireExplicitImplementation]
 	public interface IFileSystemExternalContent
 	{
-		public bool InstallContentIfRequired(ModData modData);
+		bool InstallContentIfRequired(ModData modData);
 	}
 
 	public class DefaultFileSystemLoader : IFileSystemLoader

OpenRA.Mods.Common/ItchIntegration.cs

@@ -19,7 +19,7 @@ namespace OpenRA.Mods.Common
 {
 	public class ItchIntegration : IGlobalModData
 	{
-		class User
+		sealed class User
 		{
 			[JsonProperty("url")]
 			public string Url { get; set; }
@@ -43,7 +43,7 @@ namespace OpenRA.Mods.Common
 			public string DisplayName { get; set; }
 		}
 
-		class Root
+		sealed class Root
 		{
 			public User User { get; set; }
 		}

OpenRA.Mods.Common/Lint/CheckFluentReferences.cs

@@ -502,7 +502,7 @@ namespace OpenRA.Mods.Common.Lint
 			}
 		}
 
-		class Keys
+		sealed class Keys
 		{
 			readonly HashSet<string> keys = new();
 			readonly List<(string Key, string Context)> keysWithContext = new();

OpenRA.Mods.Common/Lint/CheckSequences.cs

@@ -59,7 +59,7 @@ namespace OpenRA.Mods.Common.Lint
 					{
 						// Remove the "Info" suffix.
 						var traitName = traitInfo.GetType().Name;
-						traitName = traitName.Remove(traitName.Length - 4);
+						traitName = traitName[..^4];
 
 						var fields = Utility.GetFields(traitInfo.GetType());
 						foreach (var field in fields)

OpenRA.Mods.Common/Lint/CheckTraitLocation.cs

@@ -31,7 +31,7 @@ namespace OpenRA.Mods.Common.Lint
 					{
 						// Remove the "Info" suffix.
 						var traitName = traitInfo.GetType().Name;
-						traitName = traitName.Remove(traitName.Length - 4);
+						traitName = traitName[..^4];
 						var locations = traitLocation.SystemActors.ToString().Replace(", ", " or ");
 						emitError($"`{traitName}` does not belong on `{actorInfo.Key}`. It is a system trait meant for {locations}.");
 					}

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

@@ -567,7 +567,7 @@ namespace OpenRA.Mods.Common.Scripting
 			"so you must not add new triggers at the same time that you are calling this function.")]
 		public void Clear(Actor actor, string triggerName)
 		{
-			var trigger = (Trigger)Enum.Parse(typeof(Trigger), triggerName);
+			var trigger = Enum.Parse<Trigger>(triggerName);
 
 			if (actor == null)
 				throw new NullReferenceException(nameof(actor));

OpenRA.Mods.Common/Scripting/ScriptTriggers.cs

@@ -47,7 +47,7 @@ namespace OpenRA.Mods.Common.Scripting
 		public event Action<Actor, Actor> OnProducedInternal = (a, b) => { };
 		public event Action<Actor, Actor> OnOtherProducedInternal = (a, b) => { };
 
-		readonly List<Triggerable>[] triggerables = Exts.MakeArray(Enum.GetValues(typeof(Trigger)).Length, _ => new List<Triggerable>());
+		readonly List<Triggerable>[] triggerables = Exts.MakeArray(Enum.GetValues<Trigger>().Length, _ => new List<Triggerable>());
 
 		readonly struct Triggerable : IDisposable
 		{
@@ -526,7 +526,7 @@ namespace OpenRA.Mods.Common.Scripting
 
 		public void ClearAll()
 		{
-			foreach (Trigger t in Enum.GetValues(typeof(Trigger)))
+			foreach (var t in Enum.GetValues<Trigger>())
 				Clear(t);
 		}
 

OpenRA.Mods.Common/ServerTraits/SkirmishLogic.cs

@@ -22,7 +22,7 @@ namespace OpenRA.Mods.Common.Server
 {
 	public class SkirmishLogic : ServerTrait, IClientJoined, INotifySyncLobbyInfo
 	{
-		class SkirmishSlot
+		sealed class SkirmishSlot
 		{
 			[FieldLoader.Serialize(FromYamlKey = true)]
 			public readonly string Slot;

OpenRA.Mods.Common/Widgets/Logic/Editor/SaveMapLogic.cs

@@ -91,7 +91,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			var visOptionTemplate = visibilityPanel.Get<CheckboxWidget>("VISIBILITY_TEMPLATE");
 			visibilityPanel.RemoveChildren();
 
-			foreach (MapVisibility visibilityOption in Enum.GetValues(typeof(MapVisibility)))
+			foreach (var visibilityOption in Enum.GetValues<MapVisibility>())
 			{
 				// To prevent users from breaking the game only show the 'Shellmap' option when it is already set.
 				if (visibilityOption == MapVisibility.Shellmap && !map.Visibility.HasFlag(visibilityOption))
@@ -311,8 +311,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 
 			try
 			{
-				if (package == null)
-					throw new ArgumentNullException(nameof(package));
+				ArgumentNullException.ThrowIfNull(package);
 
 				map.Save(package);
 

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

@@ -102,7 +102,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			this.worldRenderer = worldRenderer;
 
 			MiniYaml yaml;
-			var keyNames = Enum.GetNames(typeof(ObserverStatsPanel));
+			var keyNames = Enum.GetNames<ObserverStatsPanel>();
 			var statsHotkeys = new HotkeyReference[keyNames.Length];
 			for (var i = 0; i < keyNames.Length; i++)
 				statsHotkeys[i] = logicArgs.TryGetValue("Statistics" + keyNames[i] + "Key", out yaml) ? modData.Hotkeys[yaml.Value] : new HotkeyReference();

OpenRA.Mods.Common/Widgets/TextFieldWidget.cs

@@ -321,7 +321,7 @@ namespace OpenRA.Mods.Common.Widgets
 					if (e.Modifiers.HasModifier(Modifiers.Ctrl) && CursorPosition < Text.Length)
 					{
 						// Write directly to the Text backing field to avoid unnecessary validation
-						text = text.Remove(CursorPosition);
+						text = text[..CursorPosition];
 						CursorPosition = CursorPosition.Clamp(0, text.Length);
 
 						OnTextEdited();
@@ -379,7 +379,7 @@ namespace OpenRA.Mods.Common.Widgets
 						if ((!isOSX && e.Modifiers.HasModifier(Modifiers.Ctrl)) || (isOSX && e.Modifiers.HasModifier(Modifiers.Alt)))
 							text = text[..CursorPosition] + text[GetNextWhitespaceIndex()..];
 						else if (isOSX && e.Modifiers.HasModifier(Modifiers.Meta))
-							text = text.Remove(CursorPosition);
+							text = text[..CursorPosition];
 						else
 							text = text.Remove(CursorPosition, 1);
 

OpenRA.Test/OpenRA.Game/CoordinateTest.cs

@@ -10,7 +10,6 @@
 #endregion
 
 using System;
-using System.Linq;
 using NUnit.Framework;
 
 namespace OpenRA.Test
@@ -21,7 +20,7 @@ namespace OpenRA.Test
 		[TestCase(TestName = "Test CPos and MPos conversion and back again.")]
 		public void CoarseToMapProjection()
 		{
-			foreach (var gridType in Enum.GetValues(typeof(MapGridType)).Cast<MapGridType>())
+			foreach (var gridType in Enum.GetValues<MapGridType>())
 			{
 				for (var x = 0; x < 12; x++)
 				{

OpenRA.Test/OpenRA.Game/VariableExpressionTest.cs

@@ -44,9 +44,8 @@ namespace OpenRA.Test
 
 		void AssertParseFailure(string expression, string errorMessage)
 		{
-			var actualErrorMessage = Assert.Throws(typeof(InvalidDataException),
-				() => new IntegerExpression(expression).Evaluate(testValues),
-				expression).Message;
+			var actualErrorMessage = Assert.Throws<InvalidDataException>(
+				() => new IntegerExpression(expression).Evaluate(testValues), expression).Message;
 			Assert.That(errorMessage, Is.EqualTo(actualErrorMessage), expression + "   ===>   " + actualErrorMessage);
 		}