Fix CA1816

OpenRA.Game/Graphics/SpriteCache.cs

@@ -18,7 +18,7 @@ using OpenRA.Primitives;
 
 namespace OpenRA.Graphics
 {
-	public class SpriteCache : IDisposable
+	public sealed class SpriteCache : IDisposable
 	{
 		public readonly Dictionary<SheetType, SheetBuilder> SheetBuilders;
 		readonly ISpriteLoader[] loaders;

OpenRA.Game/Manifest.cs

@@ -65,7 +65,7 @@ namespace OpenRA
 	}
 
 	/// <summary>Describes what is to be loaded in order to run a mod.</summary>
-	public class Manifest : IDisposable
+	public sealed class Manifest : IDisposable
 	{
 		public readonly string Id;
 		public readonly IReadOnlyPackage Package;

OpenRA.Game/Map/Map.cs

@@ -149,7 +149,7 @@ namespace OpenRA
 		}
 	}
 
-	public class Map : IReadOnlyFileSystem, IDisposable
+	public sealed class Map : IReadOnlyFileSystem, IDisposable
 	{
 		public const int SupportedMapFormat = 11;
 		public const int CurrentMapFormat = 12;

OpenRA.Game/Map/MapPreview.cs

@@ -61,7 +61,7 @@ namespace OpenRA
 		public readonly int mapformat;
 	}
 
-	public class MapPreview : IDisposable, IReadOnlyFileSystem
+	public sealed class MapPreview : IDisposable, IReadOnlyFileSystem
 	{
 		/// <summary>Wrapper that enables map data to be replaced in an atomic fashion.</summary>
 		sealed class InnerData