Switch to `string.Replace(char, char)` and `string.LastIndexOf(char)`

src/BizHawk.Client.Common/movie/bk2/Bk2Movie.IO.cs

@@ -23,7 +23,7 @@ namespace BizHawk.Client.Common
 			}
 
 			var backupName = Filename;
-			backupName = backupName.Insert(Filename.LastIndexOf(".", StringComparison.Ordinal), $".{DateTime.Now:yyyy-MM-dd HH.mm.ss}");
+			backupName = backupName.Insert(Filename.LastIndexOf('.'), $".{DateTime.Now:yyyy-MM-dd HH.mm.ss}");
 			backupName = Path.Combine(Session.BackupDirectory, Path.GetFileName(backupName));
 
 			Write(backupName, isBackup: true);

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -791,7 +791,7 @@ namespace BizHawk.Client.EmuHawk
 					OSTailoredCode.WindowsVersion._11 => null,
 					OSTailoredCode.WindowsVersion._10 when win10PlusVersion! < new Version(10, 0, 19044) => $"Quick reminder: Your copy of Windows 10 (build {win10PlusVersion.Build}) is no longer supported by Microsoft.\nEmuHawk will probably continue working, but please update to at least 21H2 for increased security.",
 					OSTailoredCode.WindowsVersion._10 => null,
-					_ => $"Quick reminder: Windows {winVersion.ToString().RemovePrefix('_').Replace("_", ".")} is no longer supported by Microsoft.\nEmuHawk will probably continue working, but please get a new operating system for increased security (either Windows 10+ or a GNU+Linux distro)."
+					_ => $"Quick reminder: Windows {winVersion.ToString().RemovePrefix('_').Replace('_', '.')} is no longer supported by Microsoft.\nEmuHawk will probably continue working, but please get a new operating system for increased security (either Windows 10+ or a GNU+Linux distro)."
 				};
 				if (message is not null)
 				{

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

@@ -101,7 +101,7 @@ namespace BizHawk.Client.EmuHawk
 				_inputManager.StickyXorAdapter,
 				name,
 				RangeX,
-				!string.IsNullOrEmpty(secondaryName) ? secondaryName : Name.Replace("X", "Y"),
+				string.IsNullOrEmpty(secondaryName) ? Name.Replace('X', 'Y') : secondaryName,
 				RangeY
 			);
 

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

@@ -94,7 +94,7 @@ namespace BizHawk.Emulation.Common
 
 		public AnalogSchema(int x, int y, string nameX)
 			: base(new Point(x, y), nameX)
-			=> SecondaryName = nameX.Replace("X", "Y");
+			=> SecondaryName = nameX.Replace('X', 'Y');
 	}
 
 	/// <summary>An (X, Y) pair intended to be a screen coordinate (for zappers, mouse, stylus, etc.)</summary>
@@ -111,9 +111,7 @@ namespace BizHawk.Emulation.Common
 		/// <remarks>Using this ctor, the valid ranges for the X and Y axes are taken to be <c>(0..TargetSize.Width)</c> and <c>(0..TargetSize.Height)</c>.</remarks>
 		public TargetedPairSchema(int x, int y, string nameX)
 			: base(new Point(x, y), nameX)
-		{
-			SecondaryName = nameX.Replace("X", "Y");
-		}
+			=> SecondaryName = nameX.Replace('X', 'Y');
 
 		/// <remarks>Using this ctor, the valid ranges for the X and Y axes are taken to be <c>(0..maxX)</c> and <c>(0..maxY)</c>.</remarks>
 		public TargetedPairSchema(int x, int y, string nameX, int maxX, int maxY)