Establish basic style analyzer rules (#3759)

* Fix analyzer nullable error

can't disable them in CA1305 xdd

* .editorconfig -> .globalconfig

* Add basic set of style analyzer rules

* dotnet format output

* Some additional fixes

* Apply manual simplification

* Transform some enum comparisons

* fix typo

* add TODO

.editorconfig

@@ -12,19 +12,107 @@ csharp_indent_switch_labels = true
 csharp_indent_case_contents = true
 csharp_indent_labels = one_less_than_current
 
-# Globalization rules
+# Style rules
-dotnet_code_quality.CA1305.excluded_symbol_names = T:System.Byte|T:System.SByte|T:System.Int16|T:System.UInt16|T:System.Int32|T:System.UInt32|T:System.Int64|T:System.UInt64|T:System.String|T:System.Text.StringBuilder|T:System.Convert
+# Can't be in .globalconfig because dotnet format doesn't respect that https://github.com/dotnet/format/issues/1643
 
-dotnet_diagnostic.CA1305.severity = error
+# Remove unnecessary cast
-dotnet_diagnostic.CA2101.severity = suggestion
+dotnet_diagnostic.IDE0004.severity = warning
+# Remove unnecessary import
+dotnet_diagnostic.IDE0005.severity = warning
+# Use var instead of explicit type
+dotnet_diagnostic.IDE0007.severity = suggestion
+# Use explicit type instead of var
+dotnet_diagnostic.IDE0008.severity = suggestion
+# Inline variable declaration
+dotnet_diagnostic.IDE0018.severity = warning
+# Use pattern matching to avoid as followed by a null check
+dotnet_diagnostic.IDE0019.severity = warning
+# Use pattern matching to avoid is check followed by a cast (with variable)
+dotnet_diagnostic.IDE0020.severity = warning
+# Use expression body for methods
+dotnet_diagnostic.IDE0022.severity = suggestion
+# Use expression body for properties
+dotnet_diagnostic.IDE0025.severity = suggestion
+# Use expression body for indexers
+dotnet_diagnostic.IDE0026.severity = suggestion
+# Use expression body for accessors
+dotnet_diagnostic.IDE0027.severity = suggestion
+# Null check can be simplified
+dotnet_diagnostic.IDE0029.severity = warning
+# Null check can be simplified
+dotnet_diagnostic.IDE0030.severity = warning
+# Use null propagation
+dotnet_diagnostic.IDE0031.severity = warning
+# Use auto property
+dotnet_diagnostic.IDE0032.severity = suggestion
+# Simplify default expression
+dotnet_diagnostic.IDE0034.severity = suggestion
+# Use pattern matching to avoid is check followed by a cast (without variable)
+dotnet_diagnostic.IDE0038.severity = warning
+# Use is null check
+dotnet_diagnostic.IDE0041.severity = warning
+# Deconstruct variable declaration
+dotnet_diagnostic.IDE0042.severity = suggestion
+# dotnet_diagnostic.IDE0049.severity = error # see SA1121
+# Remove unused private member
+dotnet_diagnostic.IDE0051.severity = suggestion
+# Remove unread private member
+dotnet_diagnostic.IDE0052.severity = silent # TODO: should be warning imo, but there's too much violation currently
+# Use compound assignment
+dotnet_diagnostic.IDE0054.severity = warning
+# Use index operator
+dotnet_diagnostic.IDE0056.severity = warning
+# Use range operator
+dotnet_diagnostic.IDE0057.severity = warning
+# Use simple using statement
+dotnet_diagnostic.IDE0063.severity = suggestion
+# Make struct fields writable
+dotnet_diagnostic.IDE0064.severity = error
+# using directive placement
+dotnet_diagnostic.IDE0065.severity = error
+# Use switch expression
+dotnet_diagnostic.IDE0066.severity = suggestion
+# Use System.HashCode.Combine
+dotnet_diagnostic.IDE0070.severity = warning
+# Simplify interpolation
+dotnet_diagnostic.IDE0071.severity = suggestion
+# Use coalesce compound assignment
+dotnet_diagnostic.IDE0074.severity = suggestion
+# Use pattern matching
+dotnet_diagnostic.IDE0078.severity = suggestion
+# Convert typeof to nameof
+dotnet_diagnostic.IDE0082.severity = warning
+# Use pattern matching (not operator)
+dotnet_diagnostic.IDE0083.severity = warning
+# Simplify new expression
+dotnet_diagnostic.IDE0090.severity = suggestion
+# Remove unnecessary equality operator
+dotnet_diagnostic.IDE0100.severity = warning
+# Remove unnecessary discard
+dotnet_diagnostic.IDE0110.severity = warning
+# Simplify LINQ expression
+dotnet_diagnostic.IDE0120.severity = error
+# Namespace does not match folder structure
+dotnet_diagnostic.IDE0130.severity = silent # should be warning imo
+# Use tuple to swap values
+dotnet_diagnostic.IDE0180.severity = suggestion
+# Use UTF-8 string literal
+dotnet_diagnostic.IDE0230.severity = warning
+# Nullable directive is redundant
+dotnet_diagnostic.IDE0240.severity = warning
+# Nullable directive is unnecessary
+dotnet_diagnostic.IDE0241.severity = warning
+# Struct can be made 'readonly'
+dotnet_diagnostic.IDE0250.severity = suggestion
+# Use pattern matching
+dotnet_diagnostic.IDE0260.severity = suggestion
+# Use nameof
+dotnet_diagnostic.IDE0280.severity = error
 
-# Performance rules
+csharp_style_var_when_type_is_apparent = true
-dotnet_code_quality.CA1826.exclude_ordefault_methods = true
+csharp_style_var_elsewhere = true
 
-dotnet_diagnostic.CA1805.severity = silent
+csharp_style_expression_bodied_methods = when_on_single_line
-dotnet_diagnostic.CA1822.severity = silent
+csharp_style_expression_bodied_properties = when_on_single_line
-dotnet_diagnostic.CA1838.severity = suggestion
+csharp_style_expression_bodied_indexers = when_on_single_line
-
+csharp_style_expression_bodied_accessors = when_on_single_line
-# Usage rules
-dotnet_diagnostic.CA1816.severity = none
-dotnet_diagnostic.CA2201.severity = suggestion

.globalconfig

@@ -0,0 +1,18 @@
+is_global = true
+
+# Globalization rules
+dotnet_code_quality.CA1305.excluded_symbol_names = T:System.Byte|T:System.SByte|T:System.Int16|T:System.UInt16|T:System.Int32|T:System.UInt32|T:System.Int64|T:System.UInt64|T:System.String|T:System.Text.StringBuilder|T:System.Convert
+
+dotnet_diagnostic.CA1305.severity = error
+dotnet_diagnostic.CA2101.severity = suggestion
+
+# Performance rules
+dotnet_code_quality.CA1826.exclude_ordefault_methods = true
+
+dotnet_diagnostic.CA1805.severity = silent
+dotnet_diagnostic.CA1822.severity = silent
+dotnet_diagnostic.CA1838.severity = suggestion
+
+# Usage rules
+dotnet_diagnostic.CA1816.severity = none
+dotnet_diagnostic.CA2201.severity = suggestion

Common.props

@@ -6,6 +6,7 @@
 		<AnalysisModeReliability>Recommended</AnalysisModeReliability>
 		<AnalysisModePerformance>Recommended</AnalysisModePerformance>
 		<AnalysisModeUsage>Recommended</AnalysisModeUsage>
+		<EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
 		<CodeAnalysisRuleSet>$(MSBuildProjectDirectory)/../../Common.ruleset</CodeAnalysisRuleSet>
 		<ContinuousIntegrationBuild Condition=" '$(GITLAB_CI)' != '' Or '$(APPVEYOR)' != '' ">true</ContinuousIntegrationBuild>
 		<EnableNETAnalyzers>true</EnableNETAnalyzers>

src/BizHawk.BizInvoke/BizExvoker.cs

@@ -67,8 +67,7 @@ namespace BizHawk.BizInvoke
 
 				foreach (var a in methods)
 				{
-					MethodBuilder unused;
+					var delegateType = BizInvokeUtilities.CreateDelegateType(a.Info, a.Attr!.CallingConvention, typeBuilder, out _).CreateType()!;
-					var delegateType = BizInvokeUtilities.CreateDelegateType(a.Info, a.Attr!.CallingConvention, typeBuilder, out unused).CreateType()!;
 					DelegateTypes.Add(new StoredDelegateInfo(a.Info, delegateType, a.Attr.EntryPoint ?? a.Info.Name));
 				}
 				StorageType = typeBuilder.CreateType()!;

src/BizHawk.BizInvoke/CallingConventionAdapter.cs

@@ -167,7 +167,7 @@ namespace BizHawk.BizInvoke
 			{
 				WaterboxWrapper = OSTailoredCode.IsUnixHost
 					? new NativeConvention()
-					: (ICallingConventionAdapter)new MsHostSysVGuest();
+					: new MsHostSysVGuest();
 			}
 
 			private readonly Dictionary<Delegate, int>? _slots;
@@ -247,7 +247,7 @@ namespace BizHawk.BizInvoke
 			public MsHostSysVGuest()
 			{
 				const int size = 4 * 1024 * 1024;
-				_memory = new((ulong)size);
+				_memory = new(size);
 				_refs = new WeakReference[size / BlockSize];
 			}
 

src/BizHawk.BizInvoke/MemoryBlock.cs

@@ -1,7 +1,5 @@
 using System;
 using System.IO;
-using System.Linq;
-using System.Runtime.InteropServices;
 using BizHawk.Common;
 
 namespace BizHawk.BizInvoke
@@ -19,7 +17,7 @@ namespace BizHawk.BizInvoke
 			Size = WaterboxUtils.AlignUp(size);
 
 			_pal = OSTailoredCode.IsUnixHost
-				? (IMemoryBlockPal)new MemoryBlockLinuxPal(Size)
+				? new MemoryBlockLinuxPal(Size)
 				: new MemoryBlockWindowsPal(Size);
 			Start = _pal!.Start;
 			EndExclusive = Start + Size;

src/BizHawk.BizInvoke/MemoryViewStream.cs

@@ -1,6 +1,5 @@
 using System;
 using System.IO;
-using System.Runtime.InteropServices;
 using BizHawk.Common;
 
 namespace BizHawk.BizInvoke

src/BizHawk.BizInvoke/POSIXLibC.cs

@@ -1,8 +1,6 @@
 using System;
 using System.Runtime.InteropServices;
 
-using static BizHawk.BizInvoke.MemoryBlock;
-
 namespace BizHawk.BizInvoke
 {
 	public static class POSIXLibC

src/BizHawk.Bizware.BizwareGL/BitmapBuffer.cs

@@ -527,7 +527,7 @@ namespace BizHawk.Bizware.BizwareGL
 			k--;
 			for (var i = 1; i < 32; i <<= 1)
 			{
-				k = k | k >> i;
+				k |= k >> i;
 			}
 
 			var candidate = k + 1;

src/BizHawk.Bizware.Graphics/OpenGL/SDL2OpenGLContext.cs

@@ -1,7 +1,5 @@
 using System;
 
-using Silk.NET.OpenGL.Legacy;
-
 using static SDL2.SDL;
 
 namespace BizHawk.Bizware.Graphics

src/BizHawk.Client.Common/Api/Classes/EmuClientApi.cs

@@ -1,8 +1,6 @@
 using System;
 using System.Drawing;
 using System.IO;
-
-using BizHawk.Common;
 using BizHawk.Emulation.Common;
 
 namespace BizHawk.Client.Common

src/BizHawk.Client.Common/Api/Classes/JoypadApi.cs

@@ -58,7 +58,7 @@ namespace BizHawk.Client.Common
 			// ALL button names with P{controller} prefixes
 			foreach (var button in _inputManager.ActiveController.ToBoolButtonNameList(controller))
 			{
-				Set(button, buttons.TryGetValue(button, out var state) ? state : (bool?) null, controller);
+				Set(button, buttons.TryGetValue(button, out var state) ? state : null, controller);
 			}
 		}
 

src/BizHawk.Client.Common/Api/Classes/MemoryApi.cs

@@ -3,7 +3,6 @@ using System.Collections.Generic;
 using System.Linq;
 
 using BizHawk.Common;
-using BizHawk.Common.BufferExtensions;
 using BizHawk.Emulation.Common;
 
 namespace BizHawk.Client.Common

src/BizHawk.Client.Common/Api/HttpCommunication.cs

@@ -1,5 +1,3 @@
-#pragma warning disable CA2007
-
 using System;
 using System.Collections.Generic;
 using System.Net.Http;

src/BizHawk.Client.Common/DisplayManager/DisplayManagerBase.cs

@@ -763,7 +763,6 @@ namespace BizHawk.Client.Common
 			}
 
 			var videoProvider = job.VideoProvider;
-			var glTextureProvider = videoProvider as IGLTextureProvider;
 			var simulate = job.Simulate;
 			var chainOutsize = job.ChainOutsize;
 
@@ -824,7 +823,7 @@ namespace BizHawk.Client.Common
 			Texture2d videoTexture = null;
 			if (!simulate)
 			{
-				if (glTextureProvider != null && _gl.DispMethodEnum == EDispMethod.OpenGL)
+				if (videoProvider is IGLTextureProvider glTextureProvider && _gl.DispMethodEnum == EDispMethod.OpenGL)
 				{
 					// FYI: this is a million years from happening on n64, since it's all geriatric non-FBO code
 					videoTexture = _gl.WrapGLTexture2d(new(glTextureProvider.GetGLTexture()), bufferWidth, bufferHeight);

src/BizHawk.Client.Common/DisplayManager/IBlitter.cs

@@ -1,7 +1,5 @@
 using System.Drawing;
 
-using BizHawk.Bizware.BizwareGL;
-
 namespace BizHawk.Client.Common
 {
 	/// <summary>

src/BizHawk.Client.Common/DisplayManager/OSDManager.cs

@@ -3,8 +3,6 @@ using System.Linq;
 using System.Text;
 using System.Drawing;
 using System.Collections.Generic;
-
-using BizHawk.Bizware.BizwareGL;
 using BizHawk.Emulation.Common;
 
 namespace BizHawk.Client.Common

src/BizHawk.Client.Common/lua/CommonLibs/SQLiteLuaLibrary.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
-using System.Linq;
 
 // ReSharper disable UnusedMember.Global
 namespace BizHawk.Client.Common

src/BizHawk.Client.Common/lua/LuaHelperLibs/NESLuaLibrary.cs

@@ -143,7 +143,7 @@ namespace BizHawk.Client.Common
 					nhs.DispBackground = show;
 					Settings = nhs;
 					break;
-				case QuickNES.QuickNESSettings _:
+				case QuickNES.QuickNESSettings:
 					return;
 				default:
 					throw new InvalidOperationException();
@@ -209,7 +209,7 @@ namespace BizHawk.Client.Common
 
 					Settings = nhs;
 					break;
-				case QuickNES.QuickNESSettings _:
+				case QuickNES.QuickNESSettings:
 					return;
 				default:
 					throw new InvalidOperationException();

src/BizHawk.Client.Common/movie/tasproj/StateDictionary.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Text;
 using System.IO;
 using BizHawk.Common;
 

src/BizHawk.Client.Common/movie/tasproj/TasLagLog.cs

@@ -15,7 +15,7 @@ namespace BizHawk.Client.Common
 			get
 			{
 				var result = _lagLog.TryGetValue(frame, out var lag);
-				return result ? (bool?)lag : null;
+				return result ? lag : null;
 			}
 
 			set

src/BizHawk.Client.Common/rewind/ZeldaWinder.cs

@@ -1,6 +1,5 @@
 using System;
 using System.IO;
-using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 using BizHawk.Common;
 using BizHawk.Emulation.Common;

src/BizHawk.Client.Common/tools/Cheat.cs

@@ -67,9 +67,9 @@ namespace BizHawk.Client.Common
 
 		public long? Address => _watch.Address;
 
-		public int? Value => IsSeparator ? (int?)null : _val;
+		public int? Value => IsSeparator ? null : _val;
 
-		public bool? BigEndian => IsSeparator ? (bool?)null : _watch.BigEndian;
+		public bool? BigEndian => IsSeparator ? null : _watch.BigEndian;
 
 		public int? Compare => _compare.HasValue && !IsSeparator ? _compare : null;
 
@@ -304,7 +304,7 @@ namespace BizHawk.Client.Common
 		public static bool operator ==(Cheat a, Cheat b)
 		{
 			// If one is null, but not both, return false.
-			if ((object)a == null || (object)b == null)
+			if (a is null || b is null)
 			{
 				return false;
 			}
@@ -320,7 +320,7 @@ namespace BizHawk.Client.Common
 		public static bool operator ==(Cheat a, Watch b)
 		{
 			// If one is null, but not both, return false.
-			if ((object)a == null || (object)b == null)
+			if (a is null || b is null)
 			{
 				return false;
 			}

src/BizHawk.Client.Common/tools/Watch/ByteWatch.cs

@@ -141,7 +141,7 @@ namespace BizHawk.Client.Common
 		/// Get a string representation of difference
 		/// between current value and the previous one
 		/// </summary>
-		public override string Diff => $"{_value - (short)_previous:+#;-#;0}";
+		public override string Diff => $"{_value - _previous:+#;-#;0}";
 
 		/// <summary>
 		/// Returns true if the Watch is valid, false otherwise

src/BizHawk.Client.Common/tools/Watch/Watch.cs

@@ -150,7 +150,7 @@ namespace BizHawk.Client.Common
 		/// <returns>True if both watch are equals; otherwise, false</returns>
 		public static bool operator ==(Watch a, Watch b)
 		{
-			if (ReferenceEquals(a, null) || ReferenceEquals(b, null))
+			if (a is null || b is null)
 			{
 				return false;
 			}
@@ -171,7 +171,7 @@ namespace BizHawk.Client.Common
 		/// <returns>True if they are equals; otherwise, false</returns>
 		public static bool operator ==(Watch a, Cheat b)
 		{
-			if (ReferenceEquals(a, null) || ReferenceEquals(b, null))
+			if (a is null || b is null)
 			{
 				return false;
 			}
@@ -325,7 +325,7 @@ namespace BizHawk.Client.Common
 		/// <returns>True if both object are equals; otherwise, false</returns>
 		public bool Equals(Watch other)
 		{
-			if (ReferenceEquals(other, null))
+			if (other is null)
 			{
 				return false;
 			}
@@ -342,7 +342,7 @@ namespace BizHawk.Client.Common
 		/// <returns>True if both object are equals; otherwise, false</returns>
 		public bool Equals(Cheat other)
 		{
-			return !ReferenceEquals(other, null)
+			return other is not null
 				&& _domain == other.Domain
 				&& Address == other.Address
 				&& Size == other.Size;

src/BizHawk.Client.Common/tools/Watch/WatchList/WatchEqualityComparer.cs

@@ -18,12 +18,12 @@ namespace BizHawk.Client.Common
 			/// <returns>True if <see cref="Watch"/> are equal; otherwise, false</returns>
 			public bool Equals(Watch x, Watch y)
 			{
-				if (ReferenceEquals(x, null))
+				if (x is null)
 				{
-					return ReferenceEquals(y, null);
+					return y is null;
 				}
 
-				if (ReferenceEquals(y, null))
+				if (y is null)
 				{
 					return false;
 				}

src/BizHawk.Client.Common/tools/Watch/WordWatch.cs

@@ -146,7 +146,7 @@ namespace BizHawk.Client.Common
 		/// Get a string representation of difference
 		/// between current value and the previous one
 		/// </summary>
-		public override string Diff => $"{_value - (int)_previous:+#;-#;0}";
+		public override string Diff => $"{_value - _previous:+#;-#;0}";
 
 		/// <summary>
 		/// Returns true if the Watch is valid, false otherwise

src/BizHawk.Client.DiscoHawk/Program.cs

@@ -3,9 +3,6 @@ using System.Runtime.InteropServices;
 using System.Reflection;
 using System.Collections.Generic;
 using System.IO;
-
-using BizHawk.Common;
-using BizHawk.Common.PathExtensions;
 using BizHawk.Emulation.DiscSystem;
 
 using OSTC = EXE_PROJECT.OSTailoredCode;

src/BizHawk.Client.EmuHawk/AVOut/AviWriter.cs

@@ -644,7 +644,7 @@ namespace BizHawk.Client.EmuHawk
 					IntPtr* pStream = &stream;
 					AVIWriterImports.AVICOMPRESSOPTIONS* popts = _popts;
 					AVIWriterImports.AVICOMPRESSOPTIONS** ppopts = &popts;
-					return AVIWriterImports.AVISaveOptions(owner, 0, 1, (void*)pStream, (void*)ppopts);
+					return AVIWriterImports.AVISaveOptions(owner, 0, 1, pStream, ppopts);
 				}
 			}
 
@@ -654,10 +654,10 @@ namespace BizHawk.Client.EmuHawk
 			public void OpenFile(string destPath, Parameters parameters, CodecToken videoCodecToken)
 			{
 				static int mmioFOURCC(string str) => (
-					((int)(byte)(str[0]))
+					(byte)(str[0])
-					| ((int)(byte)(str[1]) << 8)
+					| ((byte)(str[1]) << 8)
-					| ((int)(byte)(str[2]) << 16)
+					| ((byte)(str[2]) << 16)
-					| ((int)(byte)(str[3]) << 24)
+					| ((byte)(str[3]) << 24)
 				);
 
 				this._parameters = parameters;

src/BizHawk.Client.EmuHawk/AVOut/JMDWriter.cs

@@ -9,7 +9,6 @@ using System.Threading;
 using BizHawk.Client.Common;
 
 using BizHawk.Emulation.Common;
-using BizHawk.Common;
 
 namespace BizHawk.Client.EmuHawk
 {

src/BizHawk.Client.EmuHawk/AVOut/SynclessRecordingTools.cs

@@ -51,8 +51,8 @@ namespace BizHawk.Client.EmuHawk
 			foreach (var line in lines)
 			{
 				int idx = line.IndexOf('=');
-				string key = line.Substring(0, idx);
+				string key = line[..idx];
-				string value = line.Substring(idx + 1, line.Length - (idx + 1));
+				string value = line[(idx + 1)..];
 				if (key == "framesdir")
 				{
 					framesDir = value;

src/BizHawk.Client.EmuHawk/ArchiveChooser.cs

@@ -136,7 +136,7 @@ namespace BizHawk.Client.EmuHawk
 			catch (ArgumentException ex)
 			{
 				string errMsg = ex.Message;
-				errMsg = errMsg.Substring(errMsg.IndexOf('-') + 2);
+				errMsg = errMsg[(errMsg.IndexOf('-') + 2)..];
 
 				// Balloon is bugged on first invocation
 				_errorBalloon.Show($"Error parsing RegEx: {errMsg}", tb);

src/BizHawk.Client.EmuHawk/CustomControls/HexTextBox.cs

@@ -285,7 +285,7 @@ namespace BizHawk.Client.EmuHawk
 
 		public void SetFromRawInt(int? val)
 		{
-			Text = val.HasValue ? val.ToString() : "";
+			Text = val?.ToString() ?? "";
 		}
 	}
 }

src/BizHawk.Client.EmuHawk/CustomControls/InputRoll/Cell.cs

@@ -37,7 +37,7 @@ namespace BizHawk.Client.EmuHawk
 
 		public static bool operator ==(Cell a, Cell b)
 		{
-			return a?.Equals(b) ?? ReferenceEquals(b, null);
+			return a?.Equals(b) ?? b is null;
 		}
 
 		public static bool operator !=(Cell a, Cell b)

src/BizHawk.Client.EmuHawk/CustomControls/MsgBox.cs

@@ -2,8 +2,6 @@
 using System.Drawing;
 using System.Windows.Forms;
 
-using BizHawk.Common;
-
 // http://www.codeproject.com/Articles/154680/A-customizable-NET-WinForms-Message-Box
 namespace BizHawk.Client.EmuHawk.CustomControls
 {

src/BizHawk.Client.EmuHawk/Extensions/CoreExtensions.cs

@@ -9,7 +9,6 @@ using BizHawk.Emulation.Cores.Consoles.Sega.gpgx;
 using BizHawk.Emulation.Cores.Arcades.MAME;
 using BizHawk.Emulation.Cores.Consoles.Nintendo.NDS;
 using BizHawk.Emulation.Cores.Nintendo.GBA;
-using BizHawk.Emulation.Cores.Sega.MasterSystem;
 
 namespace BizHawk.Client.EmuHawk.CoreExtensions
 {

src/BizHawk.Client.EmuHawk/LogWindow.cs

@@ -92,7 +92,7 @@ namespace BizHawk.Client.EmuHawk
 						if (invoked)
 						{
 							//basically an easy way to post an update message which should hopefully happen before anything else happens (redraw or user interaction)
-							BeginInvoke((Action)doUpdateListSize);
+							BeginInvoke(doUpdateListSize);
 						}
 						else
 							doUpdateListSize();

src/BizHawk.Client.EmuHawk/MainForm.FileLoader.cs

@@ -1,6 +1,5 @@
 using System;
 using System.IO;
-using System.Windows.Forms;
 using System.Linq;
 using System.Collections.Generic;
 

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -1208,7 +1208,7 @@ namespace BizHawk.Client.EmuHawk
 			//NOTE: these must go together, because in the case of screen rotation, X and Y are transformed together
 			if(mouseX != null && mouseY != null)
 			{
-				var p = DisplayManager.UntransformPoint(new Point((int) mouseX.Value.Value, (int) mouseY.Value.Value));
+				var p = DisplayManager.UntransformPoint(new Point(mouseX.Value.Value, mouseY.Value.Value));
 				float x = p.X / (float)_currentVideoProvider.BufferWidth;
 				float y = p.Y / (float)_currentVideoProvider.BufferHeight;
 				finalHostController.AcceptNewAxis("WMouse X", (int) ((x * 20000) - 10000));
@@ -3810,8 +3810,6 @@ namespace BizHawk.Client.EmuHawk
 
 				IOpenAdvanced ioa = args.OpenAdvanced;
 				var oaOpenrom = ioa as OpenAdvanced_OpenRom;
-				var oaMame = ioa as OpenAdvanced_MAME;
-				var oaRetro = ioa as OpenAdvanced_Libretro;
 				var ioaRetro = ioa as IOpenAdvancedLibretro;
 
 				// we need to inform LoadRom which Libretro core to use...
@@ -3846,7 +3844,7 @@ namespace BizHawk.Client.EmuHawk
 				// we need to replace the path in the OpenAdvanced with the canonical one the user chose.
 				// It can't be done until loader.LoadRom happens (for CanonicalFullPath)
 				// i'm not sure this needs to be more abstractly engineered yet until we have more OpenAdvanced examples
-				if (oaRetro != null)
+				if (ioa is OpenAdvanced_Libretro oaRetro)
 				{
 					oaRetro.token.Path = loader.CanonicalFullPath;
 				}
@@ -3856,7 +3854,7 @@ namespace BizHawk.Client.EmuHawk
 					oaOpenrom.Path = loader.CanonicalFullPath;
 				}
 
-				if (oaMame != null)
+				if (ioa is OpenAdvanced_MAME oaMame)
 				{
 					oaMame.Path = loader.CanonicalFullPath;
 				}
@@ -3871,7 +3869,7 @@ namespace BizHawk.Client.EmuHawk
 					InputManager.SyncControls(Emulator, MovieSession, Config);
 					_multiDiskMode = false;
 
-					if (oaOpenrom != null && Path.GetExtension(oaOpenrom.Path.Replace("|", "")).ToLowerInvariant() == ".xml" && !(Emulator is LibsnesCore))
+					if (oaOpenrom != null && Path.GetExtension(oaOpenrom.Path.Replace("|", "")).ToLowerInvariant() == ".xml" && Emulator is not LibsnesCore)
 					{
 						// this is a multi-disk bundler file
 						// determine the xml assets and create RomStatusDetails for all of them

src/BizHawk.Client.EmuHawk/RetroAchievements/RAIntegrationDownloaderForm.cs

@@ -1,6 +1,5 @@
 using System;
 using System.IO;
-using System.Linq;
 using System.Threading;
 using System.Windows.Forms;
 

src/BizHawk.Client.EmuHawk/RetroAchievements/RetroAchievements.GameVerification.cs

@@ -119,7 +119,7 @@ namespace BizHawk.Client.EmuHawk
 							// end of the path has ;
 							var end = exePath.IndexOf(';');
 							if (end < 0) break;
-							exePath = exePath.Substring(index, end - index);
+							exePath = exePath[index..end];
 						}
 
 						buffer.AddRange(Encoding.ASCII.GetBytes(exePath));

src/BizHawk.Client.EmuHawk/ScreenSaver.cs

@@ -40,7 +40,7 @@ namespace BizHawk.Client.EmuHawk
 		}
 
 		private static readonly IScreenBlankTimer _screenBlankTimer = OSTailoredCode.IsUnixHost
-			? (IScreenBlankTimer) new UnixScreenBlankTimer()
+			? new UnixScreenBlankTimer()
 			: new Win32ScreenBlankTimer();
 
 		private static int ctr;

src/BizHawk.Client.EmuHawk/Sound/Sound.cs

@@ -43,7 +43,7 @@ namespace BizHawk.Client.EmuHawk
 			{
 				// if DirectSound or XAudio is chosen, use OpenAL, otherwise comply with the user's choice
 				_outputDevice = config.SoundOutputMethod == ESoundOutputMethod.Dummy
-					? (ISoundOutput) new DummySoundOutput(this)
+					? new DummySoundOutput(this)
 					: new OpenALSoundOutput(this, config.SoundDevice);
 			}
 			else

src/BizHawk.Client.EmuHawk/Throttle.cs

@@ -139,7 +139,7 @@ namespace BizHawk.Client.EmuHawk
 
 		private static readonly Func<uint, uint> TimeBeginPeriod = OSTailoredCode.IsUnixHost
 			? u => u
-			: (Func<uint, uint>) Win32Imports.timeBeginPeriod;
+			: Win32Imports.timeBeginPeriod;
 
 		private static readonly int tmethod;
 		private static readonly ulong afsfreq;

src/BizHawk.Client.EmuHawk/config/ControllerConfig/ControllerConfigPanel.cs

@@ -4,8 +4,6 @@ using System.Drawing;
 using System.Linq;
 using System.Windows.Forms;
 
-using BizHawk.Client.Common;
-
 namespace BizHawk.Client.EmuHawk
 {
 	// this is a little messy right now because of remnants of the old config system

src/BizHawk.Client.EmuHawk/config/FirmwaresConfig.cs

@@ -183,7 +183,7 @@ namespace BizHawk.Client.EmuHawk
 				lvFirmwares.Groups.Add(
 					key: sysID,
 					headerText: SystemGroupNames.TryGetValue(sysID, out var name) ? name : "FIX ME (FirmwaresConfig.cs)");
-				return lvFirmwares.Groups[lvFirmwares.Groups.Count - 1];
+				return lvFirmwares.Groups[^1];
 			}
 
 			// we'll use this font for displaying the hash, so they don't look all jagged in a long list

src/BizHawk.Client.EmuHawk/config/GB/ColorChooserForm.cs

@@ -192,7 +192,7 @@ namespace BizHawk.Client.EmuHawk
 
 				try
 				{
-					lines.Add(line.Substring(0, i), int.Parse(line.Substring(i + 1)));
+					lines.Add(line[..i], int.Parse(line[(i + 1)..]));
 				}
 				catch (FormatException)
 				{

src/BizHawk.Client.EmuHawk/config/GB/SameBoyColorChooserForm.cs

@@ -162,7 +162,7 @@ namespace BizHawk.Client.EmuHawk
 
 				try
 				{
-					lines.Add(line.Substring(0, i), int.Parse(line.Substring(i + 1)));
+					lines.Add(line[..i], int.Parse(line[(i + 1)..]));
 				}
 				catch (FormatException)
 				{

src/BizHawk.Client.EmuHawk/config/NES/NESSoundConfig.cs

@@ -1,5 +1,4 @@
 using System;
-using BizHawk.Client.Common;
 using BizHawk.Emulation.Cores.Nintendo.NES;
 using BizHawk.Emulation.Common;
 

src/BizHawk.Client.EmuHawk/debug/FirmwareAutopatchDebugToolForm.cs

@@ -23,10 +23,10 @@ namespace BizHawk.Client.EmuHawk.ForDebugging
 		public FirmwareAutopatchDebugToolForm()
 		{
 			static string LabelFragment(string hash)
-				=> $"{hash.Substring(0, 8)}... {FirmwareDatabase.FirmwareFilesByHash[hash].RecommendedName}";
+				=> $"{hash[..8]}... {FirmwareDatabase.FirmwareFilesByHash[hash].RecommendedName}";
 			List<(string Label, FirmwarePatchOption PatchOption)> patches = FirmwareDatabase.AllPatches
 				.Select(static fpo => ($"{LabelFragment(fpo.BaseHash)} --> {LabelFragment(fpo.TargetHash)}", fpo)).ToList();
-			patches.Sort(static (a, b) => a.Label.CompareTo(b.Label));
+			patches.Sort(static (a, b) => string.CompareOrdinal(a.Label, b.Label));
 			ComboBox comboPatchsets = new() { Size = new(300, 23) };
 			foreach (var tuple in patches) comboPatchsets.Items.Add(tuple.Label);
 			SzTextBoxEx txtBaseFile = new() { Size = new(224, 23) };

src/BizHawk.Client.EmuHawk/tools/Cheats/Cheats.cs

@@ -452,7 +452,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			var indices = SelectedIndices.ToList();
 			if (indices.Count == 0
-				|| indices[indices.Count - 1] == MainForm.CheatList.Count - 1) // at end already
+				|| indices[^1] == MainForm.CheatList.Count - 1) // at end already
 			{
 				return;
 			}

src/BizHawk.Client.EmuHawk/tools/HexEditor/HexEditor.cs

@@ -1374,7 +1374,7 @@ namespace BizHawk.Client.EmuHawk
 			// and add HighlightedAddress if present
 			if (_highlightedAddress.HasValue)
 			{
-				addresses[addresses.Length - 1] = _highlightedAddress.Value;
+				addresses[^1] = _highlightedAddress.Value;
 			}
 
 			// these need to be sorted. it's not just for HighlightedAddress, _secondaryHighlightedAddresses can even be jumbled
@@ -2224,7 +2224,7 @@ namespace BizHawk.Client.EmuHawk
 					{
 						ushort hi = _domain.PeekUshort(((addr+(i<<3)+(j<<1)     )^0x0), bigEndian);
 						ushort lo = _domain.PeekUshort(((addr+(i<<3)+(j<<1) + 32)^0x0), bigEndian);
-						matVals[i,j] = (int)(((hi << 16) | lo)) / 65536.0f;
+						matVals[i,j] = ((hi << 16) | lo) / 65536.0f;
 					}
 			}
 

src/BizHawk.Client.EmuHawk/tools/Lua/LuaConsole.cs

@@ -309,7 +309,7 @@ namespace BizHawk.Client.EmuHawk
 
 		private void OnLuaFileChanged(LuaFile item)
 		{
-			if (item.Enabled && LuaImp.ScriptList.Contains(item) == true)
+			if (item.Enabled && LuaImp.ScriptList.Contains(item))
 			{
 				RefreshLuaScript(item);
 			}
@@ -380,7 +380,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			while (LuaImp.ScriptList.Count > 0)
 			{
-				RemoveLuaFile(LuaImp.ScriptList[LuaImp.ScriptList.Count - 1]);
+				RemoveLuaFile(LuaImp.ScriptList[^1]);
 			}
 		}
 
@@ -1036,7 +1036,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			var indices = LuaListView.SelectedRows.ToList();
 			if (indices.Count == 0
-				|| indices[indices.Count - 1] == LuaImp.ScriptList.Count - 1) // at end already
+				|| indices[^1] == LuaImp.ScriptList.Count - 1) // at end already
 			{
 				return;
 			}
@@ -1330,7 +1330,7 @@ namespace BizHawk.Client.EmuHawk
 				var split = words[0].Split(Path.DirectorySeparatorChar);
 
 				luaListTemp.Add(LuaImp.ScriptList[i]);
-				luaListTemp[i].Name = split[split.Length - 1];
+				luaListTemp[i].Name = split[^1];
 			}
 
 			// Script, Path

src/BizHawk.Client.EmuHawk/tools/Lua/LuaLibraries.cs

@@ -5,7 +5,6 @@ using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Reflection;
-using System.Text;
 using System.Threading;
 
 using NLua;

src/BizHawk.Client.EmuHawk/tools/Macros/MacroInput.ButtonSelect.cs

@@ -59,7 +59,7 @@ namespace BizHawk.Client.EmuHawk
 				}
 			}
 
-			key = key.Substring(0, key.Length - 1);
+			key = key[..^1];
 
 			SelectedZone.InputKey = key;
 		}

src/BizHawk.Client.EmuHawk/tools/Macros/MacroInput.cs

@@ -209,7 +209,7 @@ namespace BizHawk.Client.EmuHawk
 				return;
 			}
 
-			if (!(CurrentMovie is ITasMovie))
+			if (CurrentMovie is not ITasMovie)
 			{
 				SelectedZone.Start = Emulator.Frame;
 			}
@@ -238,7 +238,7 @@ namespace BizHawk.Client.EmuHawk
 				ZonesList.Items.Add($"{loadZone.Name} - length: {loadZone.Length}");
 
 				// Options only for TasMovie
-				if (!(CurrentMovie is ITasMovie))
+				if (CurrentMovie is not ITasMovie)
 				{
 					loadZone.Replace = false;
 					loadZone.Overlay = false;

src/BizHawk.Client.EmuHawk/tools/Macros/MovieZone.cs

@@ -28,7 +28,7 @@ namespace BizHawk.Client.EmuHawk
 			}
 
 			key = key.Replace("LogKey:", "").Replace("#", "");
-			key = key.Substring(0, key.Length - 1);
+			key = key[..^1];
 
 			_inputKey = key;
 			Length = length;
@@ -41,7 +41,7 @@ namespace BizHawk.Client.EmuHawk
 			logGenerator.GenerateLogEntry(); // Reference and create all buttons.
 
 			string movieKey = logGenerator.GenerateLogKey().Replace("LogKey:", "").Replace("#", "");
-			movieKey = movieKey.Substring(0, movieKey.Length - 1);
+			movieKey = movieKey[..^1];
 			if (key == movieKey)
 			{
 				for (int i = 0; i < length; i++)
@@ -239,7 +239,7 @@ namespace BizHawk.Client.EmuHawk
 			var lg = _movieSession.Movie.LogGeneratorInstance(_movieSession.MovieController);
 			string key = lg.GenerateLogKey();
 			key = key.Replace("LogKey:", "").Replace("#", "");
-			key = key.Substring(0, key.Length - 1);
+			key = key[..^1];
 			string[] emuKeys = key.Split('|');
 			string[] macroKeys = _inputKey.Split('|');
 			foreach (var macro in macroKeys)

src/BizHawk.Client.EmuHawk/tools/MultiDiskBundler/MultiDiskBundler.cs

@@ -3,13 +3,11 @@ using System.Collections.Generic;
 using System.Drawing;
 using System.IO;
 using System.Linq;
-using System.Text;
 using System.Windows.Forms;
 using System.Xml.Linq;
 
 using BizHawk.Emulation.Common;
 using BizHawk.Client.Common;
-using BizHawk.Common;
 using BizHawk.Common.PathExtensions;
 using BizHawk.Common.StringExtensions;
 using BizHawk.Emulation.Cores.Sega.MasterSystem;
@@ -121,15 +119,13 @@ namespace BizHawk.Client.EmuHawk
 
 		private void SaveButton_Click(object sender, EventArgs e)
 		{
-			FileInfo dummy;
+			DoSave(out var dummy);
-			DoSave(out dummy);
 		}
 
 		private void SaveRunButton_Click(object sender, EventArgs e)
 		{
-			FileInfo fileInfo;
 
-			if (!DoSave(out fileInfo))
+			if (!DoSave(out var fileInfo))
 				return;
 
 			DialogResult = DialogResult.OK;

src/BizHawk.Client.EmuHawk/tools/NES/BarcodeEntry.cs

@@ -1,7 +1,5 @@
 using System;
 using System.Drawing;
-
-using BizHawk.Client.Common;
 using BizHawk.Emulation.Cores.Nintendo.NES;
 using BizHawk.Emulation.Common;
 

src/BizHawk.Client.EmuHawk/tools/NES/NESMusicRipper.cs

@@ -4,7 +4,6 @@ using System.Drawing;
 using System.IO;
 using System.IO.Compression;
 using System.Linq;
-using System.Text;
 using System.Windows.Forms;
 using System.Xml.XPath;
 using System.Xml.Linq;

src/BizHawk.Client.EmuHawk/tools/PCE/PCEBGViewer.cs

@@ -53,9 +53,9 @@ namespace BizHawk.Client.EmuHawk
 				var buf = canvas.Bat.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.WriteOnly, canvas.Bat.PixelFormat);
 				var pitch = buf.Stride / 4;
 				var begin = (int*)buf.Scan0.ToPointer();
-				var vram = (ushort*)view.Vram;
+				var vram = view.Vram;
-				var patternBuffer = (byte*)view.BackgroundCache;
+				var patternBuffer = view.BackgroundCache;
-				var palette = (int*)view.PaletteCache;
+				var palette = view.PaletteCache;
 
 				int* p = begin;
 				for (int y = 0; y < height; ++y)
@@ -118,7 +118,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			Viewer.GetGpuData(_vdcType, view =>
 			{
-				var vram = (ushort*)view.Vram;
+				var vram = view.Vram;
 				int xTile = e.X / 8;
 				int yTile = e.Y / 8;
 				int tileNo = vram[(ushort)((yTile * view.BatWidth) + xTile)] & 0x07FF;

src/BizHawk.Client.EmuHawk/tools/PCE/PCETileViewer.cs

@@ -81,8 +81,8 @@ namespace BizHawk.Client.EmuHawk
 
 				int* dest = (int*)lockData.Scan0;
 				int pitch = lockData.Stride / sizeof(int);
-				byte* src = (byte*)view.SpriteCache;
+				byte* src = view.SpriteCache;
-				int* pal = (int*)view.PaletteCache + 256 + _spPalNum * 16;
+				int* pal = view.PaletteCache + 256 + _spPalNum * 16;
 				for (int tile = 0; tile < 512; tile++)
 				{
 					int srcAddr = tile * 256;
@@ -103,8 +103,8 @@ namespace BizHawk.Client.EmuHawk
 
 				int* dest = (int*)lockData.Scan0;
 				int pitch = lockData.Stride / sizeof(int);
-				byte* src = (byte*)view.BackgroundCache;
+				byte* src = view.BackgroundCache;
-				int* pal = (int*)view.PaletteCache + _bgPalNum * 16;
+				int* pal = view.PaletteCache + _bgPalNum * 16;
 				for (int tile = 0; tile < 2048; tile++)
 				{
 					int srcAddr = tile * 64;
@@ -121,7 +121,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			Viewer.GetGpuData(checkBoxVDC2.Checked ? 1 : 0, view =>
 			{
-				int* pal = (int*)view.PaletteCache;
+				int* pal = view.PaletteCache;
 				DrawPalette(bmpViewBGPal.Bmp, pal);
 				DrawPalette(bmpViewSPPal.Bmp, pal + 256);
 			});

src/BizHawk.Client.EmuHawk/tools/TAStudio/BookmarksBranchesBox.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Collections.Generic;
 using System.ComponentModel;
 using System.Drawing;
 using System.IO;

src/BizHawk.Client.EmuHawk/tools/TAStudio/PatternsForm.cs

@@ -302,7 +302,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					if (p[i] == lastValue)
 					{
-						_counts[_counts.Count - 1]++;
+						_counts[^1]++;
 					}
 					else
 					{
@@ -335,7 +335,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					if (p[i] == lastValue)
 					{
-						_counts[_counts.Count - 1]++;
+						_counts[^1]++;
 					}
 					else
 					{

src/BizHawk.Client.EmuHawk/tools/TAStudio/TAStudio.ListView.cs

@@ -1325,7 +1325,7 @@ namespace BizHawk.Client.EmuHawk
 			else if (e.KeyCode == Keys.OemMinus || e.KeyCode == Keys.Subtract)
 			{
 				_axisTypedValue = _axisTypedValue.StartsWith('-')
-					? _axisTypedValue.Substring(1)
+					? _axisTypedValue[1..]
 					: $"-{_axisTypedValue}";
 			}
 			else if (e.KeyCode == Keys.Back)
@@ -1335,7 +1335,7 @@ namespace BizHawk.Client.EmuHawk
 					_axisTypedValue = value.ToString(NumberFormatInfo.InvariantInfo);
 				}
 
-				_axisTypedValue = _axisTypedValue.Substring(0, _axisTypedValue.Length - 1);
+				_axisTypedValue = _axisTypedValue[..^1];
 				if (_axisTypedValue == "" || _axisTypedValue == "-")
 				{
 					value = 0f;

src/BizHawk.Client.EmuHawk/tools/TAStudio/TAStudio.MenuItems.cs

@@ -469,7 +469,7 @@ namespace BizHawk.Client.EmuHawk
 						{
 							_tasClipboard.Clear();
 							int linesToPaste = lines.Length;
-							if (lines[lines.Length - 1] == "") linesToPaste--;
+							if (lines[^1] == "") linesToPaste--;
 							for (int i = 0; i < linesToPaste; i++)
 							{
 								var line = ControllerFromMnemonicStr(lines[i]);
@@ -511,7 +511,7 @@ namespace BizHawk.Client.EmuHawk
 						{
 							_tasClipboard.Clear();
 							int linesToPaste = lines.Length;
-							if (lines[lines.Length - 1] == "") linesToPaste--;
+							if (lines[^1] == "") linesToPaste--;
 							for (int i = 0; i < linesToPaste; i++)
 							{
 								var line = ControllerFromMnemonicStr(lines[i]);

src/BizHawk.Client.EmuHawk/tools/TAStudio/TAStudio.cs

@@ -11,7 +11,6 @@ using BizHawk.Client.EmuHawk.Properties;
 using BizHawk.Common;
 using BizHawk.Common.StringExtensions;
 using BizHawk.Emulation.Common;
-using BizHawk.Emulation.Cores.Nintendo.N64;
 
 namespace BizHawk.Client.EmuHawk
 {
@@ -228,7 +227,7 @@ namespace BizHawk.Client.EmuHawk
 			}
 
 			// Start Scenario 1: A regular movie is active
-			if (MovieSession.Movie.IsActive() && !(MovieSession.Movie is ITasMovie))
+			if (MovieSession.Movie.IsActive() && MovieSession.Movie is not ITasMovie)
 			{
 				var changesString = "Would you like to save the current movie before closing it?";
 				if (MovieSession.Movie.Changes)
@@ -451,8 +450,8 @@ namespace BizHawk.Client.EmuHawk
 				BoolPatterns[i] = new AutoPatternBool(1, 1);
 			}
 
-			BoolPatterns[BoolPatterns.Length - 2] = new AutoPatternBool(1, 0);
+			BoolPatterns[^2] = new AutoPatternBool(1, 0);
-			BoolPatterns[BoolPatterns.Length - 1] = new AutoPatternBool(
+			BoolPatterns[^1] = new AutoPatternBool(
 				Config.AutofireOn, Config.AutofireOff);
 
 			for (int i = fStart; i < AxisPatterns.Length - 2; i++)
@@ -460,8 +459,8 @@ namespace BizHawk.Client.EmuHawk
 				AxisPatterns[i] = new AutoPatternAxis(new[] { 1 });
 			}
 
-			AxisPatterns[AxisPatterns.Length - 2] = new AutoPatternAxis(new[] { 1 });
+			AxisPatterns[^2] = new AutoPatternAxis(new[] { 1 });
-			AxisPatterns[AxisPatterns.Length - 1] = new AutoPatternAxis(1, Config.AutofireOn, 0, Config.AutofireOff);
+			AxisPatterns[^1] = new AutoPatternAxis(1, Config.AutofireOn, 0, Config.AutofireOff);
 
 			SetUpToolStripColumns();
 		}

src/BizHawk.Client.EmuHawk/tools/ToolManager.cs

@@ -85,10 +85,10 @@ namespace BizHawk.Client.EmuHawk
 		// If the form inherits ToolFormBase, it will set base properties such as Tools, Config, etc
 		private void SetBaseProperties(IToolForm form)
 		{
-			if (!(form is FormBase f)) return;
+			if (form is not FormBase f) return;
 
 			f.Config = _config;
-			if (!(form is ToolFormBase tool)) return;
+			if (form is not ToolFormBase tool) return;
 			tool.SetToolFormBaseProps(_displayManager, _inputManager, _owner, _movieSession, this, _game);
 		}
 
@@ -121,7 +121,7 @@ namespace BizHawk.Client.EmuHawk
 				_tools.Remove(existingTool);
 			}
 
-			if (!(CreateInstance<T>(toolPath) is T newTool)) return null;
+			if (CreateInstance<T>(toolPath) is not T newTool) return null;
 
 			if (newTool is Form form) form.Owner = _owner;
 			if (!ServiceInjector.UpdateServices(_emulator.ServiceProvider, newTool)) return null; //TODO pass `true` for `mayCache` when from EmuHawk assembly
@@ -402,7 +402,7 @@ namespace BizHawk.Client.EmuHawk
 						var converter = TypeDescriptor.GetConverter(prop.PropertyType);
 						val = converter.ConvertFromString(null, CultureInfo.InvariantCulture, str);
 					}
-					else if (!(val is bool) && prop.PropertyType.IsPrimitive)
+					else if (val is not bool && prop.PropertyType.IsPrimitive)
 					{
 						// numeric constants are similarly hosed
 						val = Convert.ChangeType(val, prop.PropertyType, CultureInfo.InvariantCulture);

src/BizHawk.Client.EmuHawk/tools/VirtualPads/VirtualpadsTool.cs

@@ -128,8 +128,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			foreach (var control in ControllerPanel.Controls)
 			{
-				var vp = control as VirtualPad;
+				if (control is not VirtualPad vp)
-				if (vp == null)
 				{
 					continue;
 				}

src/BizHawk.Client.EmuHawk/tools/VirtualPads/controls/VirtualPadDiscManager.cs

@@ -37,7 +37,7 @@ namespace BizHawk.Client.EmuHawk
 
 		private void UpdateCoreAssociation()
 		{
-			if (!(_ownerEmulator is Octoshock psx))
+			if (_ownerEmulator is not Octoshock psx)
 			{
 				return;
 			}

src/BizHawk.Client.EmuHawk/tools/VirtualPads/controls/components/AnalogStickPanel.cs

@@ -170,8 +170,8 @@ namespace BizHawk.Client.EmuHawk
 
 		private void SetAnalog()
 		{
-			_stickyXorAdapter.SetAxis(XName, HasValue ? X : (int?)null);
+			_stickyXorAdapter.SetAxis(XName, HasValue ? X : null);
-			_stickyXorAdapter.SetAxis(YName, HasValue ? Y : (int?)null);
+			_stickyXorAdapter.SetAxis(YName, HasValue ? Y : null);
 			Refresh();
 		}
 

src/BizHawk.Client.EmuHawk/tools/Watch/RamWatch.cs

@@ -415,7 +415,7 @@ namespace BizHawk.Client.EmuHawk
 				foreach (var row in clipboardRows)
 				{
 					var watch = Watch.FromString(row, MemoryDomains);
-					if ((object)watch != null)
+					if (watch is not null)
 					{
 						_watches.Add(watch);
 					}
@@ -910,7 +910,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			var indices = SelectedIndices.ToList();
 			if (indices.Count == 0
-				|| indices[indices.Count - 1] == _watches.Count - 1) // at end already
+				|| indices[^1] == _watches.Count - 1) // at end already
 			{
 				return;
 			}

src/BizHawk.Client.EmuHawk/tools/Watch/WatchValueBox.cs

@@ -195,7 +195,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					default:
 					case WatchDisplayType.Signed:
-						int? val = ToRawInt() ?? 0;
+						int val = ToRawInt() ?? 0;
 						if (val == MaxSignedInt)
 						{
 							val = MinSignedInt;
@@ -307,12 +307,8 @@ namespace BizHawk.Client.EmuHawk
 				{
 					default:
 					case WatchDisplayType.Signed:
-						var val = ToRawInt();
+						int val = ToRawInt() ?? 0;
-						if (!val.HasValue)
+						if (val == MinSignedInt)
-						{
-							Text = "";
-						}
-						else if (val == MinSignedInt)
 						{
 							val = MaxSignedInt;
 						}
@@ -468,7 +464,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					default:
 					case WatchDisplayType.Signed:
-						Text = val.ToString();
+						Text = val.Value.ToString();
 						break;
 					case WatchDisplayType.Unsigned:
 						var uval = (uint)val.Value;

src/BizHawk.Common/BPSPatcher.cs

@@ -2,8 +2,6 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Text;
-
-using BizHawk.Common.BufferExtensions;
 using BizHawk.Common.CollectionExtensions;
 
 namespace BizHawk.Common

src/BizHawk.Common/Bit.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Diagnostics;
 
 namespace BizHawk.Common

src/BizHawk.Common/CustomCollections.cs

@@ -110,7 +110,7 @@ namespace BizHawk.Common
 			else
 			{
 				// All items *after* the item
-				startIndex = startIndex + 1;
+				startIndex++;
 			}
 			if (startIndex < _list.Count)
 			{

src/BizHawk.Common/Extensions/StringExtensions.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.CompilerServices;
 

src/BizHawk.Common/HawkFile/HawkFile.cs

@@ -297,7 +297,7 @@ namespace BizHawk.Common
 #if DEBUG
 			if (path.IndexOf('|') != i) Console.WriteLine($"{nameof(HawkFile)} path contains multiple '|'");
 #endif
-			return i == -1 ? ((string, string)?) null : (path.Substring(0, i), path.Substring(i + 1));
+			return i == -1 ? null : (path.Substring(0, i), path.Substring(i + 1));
 		}
 	}
 }

src/BizHawk.Common/IMonitor.cs

@@ -1,6 +1,4 @@
-using System;
+namespace BizHawk.Common
-
-namespace BizHawk.Common
 {
 	public interface IMonitor
 	{

src/BizHawk.Common/OSTailoredCode.cs

@@ -1,4 +1,6 @@
+#pragma warning disable IDE0240
 #nullable enable
+#pragma warning restore IDE0240
 
 using System;
 using System.Diagnostics;

src/BizHawk.Emulation.Common/Base Implementations/LinkedDisassemblable.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Collections.Generic;
 
 namespace BizHawk.Emulation.Common

src/BizHawk.Emulation.Common/Base Implementations/MemoryCallbackSystem.cs

@@ -5,7 +5,6 @@ using System.Linq;
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Runtime.CompilerServices;
 
 namespace BizHawk.Emulation.Common
 {

src/BizHawk.Emulation.Common/Database/FirmwarePatchData.cs

@@ -1,4 +1,3 @@
-#nullable enable
 
 using System;
 

src/BizHawk.Emulation.Common/Database/FirmwarePatchOption.cs

@@ -1,4 +1,3 @@
-#nullable enable
 
 using System.Collections.Generic;
 

src/BizHawk.Emulation.Common/Extensions.cs

@@ -2,7 +2,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.CompilerServices;

src/BizHawk.Emulation.Common/N64RomByteswapper.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Runtime.InteropServices;
 
 using BizHawk.Common;
 

src/BizHawk.Emulation.Common/SaveController.cs

@@ -3,7 +3,6 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Linq;
 
 using BizHawk.Common;
 

src/BizHawk.Emulation.Common/ServiceInjector.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using System.Reflection;
 
 using BizHawk.Common.ReflectionExtensions;

src/BizHawk.Emulation.Common/vpads_schemata/PadSchemaControl.cs

@@ -1,8 +1,6 @@
 using System.Collections.Generic;
 using System.Drawing;
 
-using BizHawk.Emulation.Common;
-
 namespace BizHawk.Emulation.Common
 {
 	public abstract class PadSchemaControl

src/BizHawk.Emulation.Cores/Arcades/MAME/LibMAME.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Runtime.InteropServices;
-using System.Text;
 
 using BizHawk.BizInvoke;
 

src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.ISettable.cs

@@ -168,7 +168,7 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 						if (hashdata.Contains("^"))
 						{
 							hashdata = hashdata.RemoveSuffix("^");
-							name = name + " (BAD DUMP)";
+							name += " (BAD DUMP)";
 						}
 
 						hashdata = hashdata.Replace("R", "CRC:").Replace("S", " SHA:");

src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.IVideoProvider.cs

@@ -1,6 +1,4 @@
 using System;
-using System.Collections.Generic;
-using System.Runtime.InteropServices;
 
 using BizHawk.Emulation.Common;
 

src/BizHawk.Emulation.Cores/CPUs/68000/Instructions/DataMovement.cs

@@ -508,7 +508,7 @@ namespace BizHawk.Emulation.Cores.Components.M68000
 			string address = DisassembleAddress(mode, reg, ref pc);
 
 			info.Mnemonic = size == 0 ? "movem.w" : "movem.l";
-			info.Args = DisassembleRegisterList0((uint)registers) + ", " + address;
+			info.Args = DisassembleRegisterList0(registers) + ", " + address;
 			info.Length = pc - info.PC;
 		}
 

src/BizHawk.Emulation.Cores/CPUs/68000/Instructions/IntegerMath.cs

@@ -1126,7 +1126,7 @@ namespace BizHawk.Emulation.Cores.Components.M68000
 			int quotient = dest / source;
 			int remainder = dest % source;
 
-			V = ((int)quotient < short.MinValue || (int)quotient > short.MaxValue);
+			V = (quotient < short.MinValue || quotient > short.MaxValue);
 			N = (quotient & 0x8000) != 0;
 			Z = quotient == 0;
 			C = false;

src/BizHawk.Emulation.Cores/CPUs/68000/Instructions/ProgramFlow.cs

@@ -58,7 +58,7 @@ namespace BizHawk.Emulation.Cores.Components.M68000
 			sbyte displacement8 = (sbyte)op;
 			int cond = (op >> 8) & 0x0F;
 
-			if (TestCondition(cond) == true)
+			if (TestCondition(cond))
 			{
 				if (displacement8 != 0)
 				{
@@ -169,7 +169,7 @@ namespace BizHawk.Emulation.Cores.Components.M68000
 
 		private void DBcc()
 		{
-			if (TestCondition((op >> 8) & 0x0F) == true)
+			if (TestCondition((op >> 8) & 0x0F))
 			{
 				PC += 2; // condition met, break out of loop
 				PendingCycles -= 12;
@@ -712,7 +712,7 @@ namespace BizHawk.Emulation.Cores.Components.M68000
 			int mode = (op >> 3) & 7;
 			int reg = (op >> 0) & 7;
 
-			if (TestCondition(cond) == true)
+			if (TestCondition(cond))
 			{
 				WriteValueB(mode, reg, -1);
 				if (mode == 0) PendingCycles -= 6;

src/BizHawk.Emulation.Cores/CPUs/68000/Instructions/Supervisor.cs

@@ -29,7 +29,7 @@ namespace BizHawk.Emulation.Cores.Components.M68000
 		{
 			int mode = (op >> 3) & 7;
 			int reg = (op >> 0) & 7;
-			WriteValueW(mode, reg, (short)SR);
+			WriteValueW(mode, reg, SR);
 			PendingCycles -= (mode == 0) ? 6 : 8 + EACyclesBW[mode, reg];
 		}
 
@@ -151,7 +151,7 @@ namespace BizHawk.Emulation.Cores.Components.M68000
 
 		private void TrapVector(int vector)
 		{
-			short sr = (short)SR;        // capture current SR.
+			short sr = SR;        // capture current SR.
 			S = true;                    // switch to supervisor mode, if not already in it.
 			A[7].s32 -= 4;               // Push PC on stack
 			WriteLong(A[7].s32, PC);

src/BizHawk.Emulation.Cores/CPUs/68000/MC68000.cs

@@ -36,7 +36,7 @@ namespace BizHawk.Emulation.Cores.Components.M68000
 			set
 			{
 				if (value == s) return;
-				if (value == true) // entering supervisor mode
+				if (value) // entering supervisor mode
 				{
 					Console.WriteLine("&^&^&^&^& ENTER SUPERVISOR MODE");
 					usp = A[7].s32;
@@ -142,7 +142,7 @@ namespace BizHawk.Emulation.Cores.Components.M68000
 				{
 					// TODO: Entering interrupt is not free. how many cycles does it take?
 					//Log.Error("CPU","****** ENTER INTERRUPT {0} *******", Interrupt);
-					short sr = (short)SR;                  // capture current SR.
+					short sr = SR;                  // capture current SR.
 					S = true;                               // switch to supervisor mode, if not already in it.
 					A[7].s32 -= 4;                          // Push PC on stack
 					WriteLong(A[7].s32, PC);

src/BizHawk.Emulation.Cores/CPUs/CP1610/CP1610.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.IO;
 using BizHawk.Common;
 using BizHawk.Emulation.Common;
 

src/BizHawk.Emulation.Cores/CPUs/FairchildF8/F3850.Operations.cs

@@ -19,7 +19,7 @@ namespace BizHawk.Emulation.Cores.Components.FairchildF8
 
 		public void IN_Func(byte dest, byte src)
 		{
-			Regs[dest] = ReadHardware((byte)(Regs[src]));
+			Regs[dest] = ReadHardware(Regs[src]);
 		}
 
 		/// <summary>

src/BizHawk.Emulation.Cores/CPUs/FairchildF8/F3850.Registers.cs

@@ -174,7 +174,7 @@ namespace BizHawk.Emulation.Cores.Components.FairchildF8
 		public bool IRQRequest
 		{
 			get => Regs[IRQR] > 0;
-			set => Regs[IRQR] = value == true ? (byte)1 : (byte)0;
+			set => Regs[IRQR] = value ? (byte)1 : (byte)0;
 		}
 
 		/// <summary>