Remove unnecessary calls to ToList (e.g. in foreach)

squashed PR #1591

BizHawk.Client.Common/RecentFiles.cs

@@ -89,17 +89,7 @@ namespace BizHawk.Client.Common
 		{
 			if (!Frozen)
 			{
-				var removed = false;
+				return recentlist.RemoveAll(recent => string.Compare(newFile, recent, StringComparison.CurrentCultureIgnoreCase) == 0) != 0; // none removed => return false
-				foreach (var recent in recentlist.ToList())
-				{
-					if (string.Compare(newFile, recent, StringComparison.CurrentCultureIgnoreCase) == 0)
-					{
-						recentlist.Remove(newFile); // intentionally keeps iterating after this to remove duplicate instances, though those should never exist in the first place
-						removed = true;
-					}
-				}
-
-				return removed;
 			}
 
 			return false;

BizHawk.Client.Common/config/Binding.cs

@@ -96,13 +96,8 @@ namespace BizHawk.Client.Common
 				}
 			}
 
-			List<Binding> entriesToRemove = (from entry in Bindings let binding = DefaultValues.FirstOrDefault(b => b.DisplayName == entry.DisplayName) where binding == null select entry).ToList();
-
 			// Remove entries that no longer exist in defaults
-			foreach (Binding entry in entriesToRemove)
+			Bindings.RemoveAll(entry => DefaultValues.All(b => b.DisplayName != entry.DisplayName));
-			{
-				Bindings.Remove(entry);
-			}
 		}
 
 		private static List<Binding> _defaultValues;

BizHawk.Client.Common/config/PathEntry.cs

@@ -119,7 +119,7 @@ namespace BizHawk.Client.Common
 			}
 
 			// Add missing displaynames
-			var missingDisplayPaths = Paths.Where(p => p.SystemDisplayName == null).ToList();
+			var missingDisplayPaths = Paths.Where(p => p.SystemDisplayName == null);
 			foreach (PathEntry path in missingDisplayPaths)
 			{
 				path.SystemDisplayName = DefaultValues.First(p => p.System == path.System).SystemDisplayName;

BizHawk.Client.Common/lua/EmuLuaLibrary.Events.cs

@@ -50,78 +50,66 @@ namespace BizHawk.Client.Common
 
 		public void CallSaveStateEvent(string name)
 		{
-			var lfs = _luaFunctions.Where(l => l.Event == "OnSavestateSave").ToList();
+			var lfs = _luaFunctions.Where(l => l.Event == "OnSavestateSave");
-			if (lfs.Any())
+			try
 			{
-				try
+				foreach (var lf in lfs)
 				{
-					foreach (var lf in lfs)
+					lf.Call(name);
-					{
-						lf.Call(name);
-					}
-				}
-				catch (Exception e)
-				{
-					Log($"error running function attached by lua function event.onsavestate\nError message: {e.Message}");
 				}
 			}
+			catch (Exception e)
+			{
+				Log($"error running function attached by lua function event.onsavestate\nError message: {e.Message}");
+			}
 		}
 
 		public void CallLoadStateEvent(string name)
 		{
-			var lfs = _luaFunctions.Where(l => l.Event == "OnSavestateLoad").ToList();
+			var lfs = _luaFunctions.Where(l => l.Event == "OnSavestateLoad");
-			if (lfs.Any())
+			try
 			{
-				try
+				foreach (var lf in lfs)
 				{
-					foreach (var lf in lfs)
+					lf.Call(name);
-					{
-						lf.Call(name);
-					}
-				}
-				catch (Exception e)
-				{
-					Log($"error running function attached by lua function event.onloadstate\nError message: {e.Message}");
 				}
 			}
+			catch (Exception e)
+			{
+				Log($"error running function attached by lua function event.onloadstate\nError message: {e.Message}");
+			}
 		}
 
 		public void CallFrameBeforeEvent()
 		{
-			var lfs = _luaFunctions.Where(l => l.Event == "OnFrameStart").ToList();
+			var lfs = _luaFunctions.Where(l => l.Event == "OnFrameStart");
-			if (lfs.Any())
+			try
 			{
-				try
+				foreach (var lf in lfs)
 				{
-					foreach (var lf in lfs)
+					lf.Call();
-					{
-						lf.Call();
-					}
-				}
-				catch (Exception e)
-				{
-					Log($"error running function attached by lua function event.onframestart\nError message: {e.Message}");
 				}
 			}
+			catch (Exception e)
+			{
+				Log($"error running function attached by lua function event.onframestart\nError message: {e.Message}");
+			}
 		}
 
 		public void CallFrameAfterEvent()
 		{
-			var lfs = _luaFunctions.Where(l => l.Event == "OnFrameEnd").ToList();
+			var lfs = _luaFunctions.Where(l => l.Event == "OnFrameEnd");
-			if (lfs.Any())
+			try
 			{
-				try
+				foreach (var lf in lfs)
 				{
-					foreach (var lf in lfs)
+					lf.Call();
-					{
-						lf.Call();
-					}
-				}
-				catch (Exception e)
-				{
-					Log($"error running function attached by lua function event.onframeend\nError message: {e.Message}");
 				}
 			}
+			catch (Exception e)
+			{
+				Log($"error running function attached by lua function event.onframeend\nError message: {e.Message}");
+			}
 		}
 
 		private bool N64CoreTypeDynarec()

BizHawk.Client.Common/movie/bk2/Bk2ControllerAdapter.cs

@@ -160,7 +160,7 @@ namespace BizHawk.Client.Common
 			{
 				var def = Global.Emulator.ControllerDefinition;
 				var trimmed = mnemonic.Replace("|", "");
-				var buttons = Definition.ControlsOrdered.SelectMany(c => c).ToList();
+				var buttons = Definition.ControlsOrdered.SelectMany(c => c);
 				var iterator = 0;
 
 				foreach (var key in buttons)

BizHawk.Client.Common/tools/CheatList.cs

@@ -222,7 +222,7 @@ namespace BizHawk.Client.Common
 
 		public void RemoveRange(IEnumerable<Cheat> cheats)
 		{
-			foreach (var cheat in cheats.ToList())
+			foreach (var cheat in cheats.ToList()) // enumerate passed IEnumerable because it may depend on the value of _cheatList
 			{
 				_cheatList.Remove(cheat);
 			}
@@ -232,12 +232,7 @@ namespace BizHawk.Client.Common
 
 		public void RemoveRange(IEnumerable<Watch> watches)
 		{
-			var removeList = _cheatList.Where(cheat => watches.Any(w => w == cheat)).ToList();
+			_cheatList.RemoveAll(cheat => watches.Any(w => w == cheat));
-			foreach (var cheat in removeList)
-			{
-				_cheatList.Remove(cheat);
-			}
-
 			Changes = true;
 		}
 

BizHawk.Client.Common/tools/RamSearchEngine.cs

@@ -341,8 +341,7 @@ namespace BizHawk.Client.Common
 			}
 
 			var addresses = watches.Select(w => w.Address);
-			var removeList = _watchList.Where(w => addresses.Contains(w.Address)).ToList();
+			_watchList.RemoveAll(w => addresses.Contains(w.Address));
-			_watchList = _watchList.Except(removeList).ToList();
 		}
 
 		public void RemoveRange(IEnumerable<int> indices)

BizHawk.Client.DBMan/DATTools/NOINTROParser.cs

@@ -188,11 +188,11 @@ namespace BizHawk.Client.DBMan
 				// process dump info flags and other info contained in []
 				if (nameString.Contains("[") && nameString.Contains("]"))
 				{
-					List<string> e = nameString.ToString().Split('[', ']').ToList();
+					var e = nameString.Split('[', ']')
-					// remove first entry (this is the bit before the [] entries start
+						.Skip(1) // remove first entry (this is the bit before the [] entries start)
-					e.RemoveAt(0);
+						.Where(s => !string.IsNullOrWhiteSpace(s)) // remove empty entries
-					// remove empty entries
+						.Distinct()
-					e = e.Where(s => !string.IsNullOrWhiteSpace(s)).Distinct().ToList();
+						.ToList();
 
 					if (e.Count > 0)
 					{

BizHawk.Client.DBMan/DATTools/TOSECParser.cs

@@ -206,11 +206,11 @@ namespace BizHawk.Client.DBMan
 				// process dump info flags and other info contained in []
 				if (nameString.Contains("[") && nameString.Contains("]"))
 				{
-					List<string> e = nameString.ToString().Split('[', ']').ToList();
+					var e = nameString.Split('[', ']')
-					// remove first entry (this is the bit before the [] entries start
+						.Skip(1) // remove first entry (this is the bit before the [] entries start)
-					e.RemoveAt(0);
+						.Where(s => !string.IsNullOrWhiteSpace(s)) // remove empty entries
-					// remove empty entries
+						.Distinct()
-					e = e.Where(s => !string.IsNullOrWhiteSpace(s)).Distinct().ToList();
+						.ToList();
 
 					if (e.Count > 0)
 					{

BizHawk.Client.EmuHawk/Api/ApiManager.cs

@@ -23,15 +23,12 @@ namespace BizHawk.Client.EmuHawk
 				.Where(t => typeof(IExternalApi).IsAssignableFrom(t))
 				.Where(t => t.IsSealed)
 				.Where(t => ServiceInjector.IsAvailable(serviceProvider, t))
-				.ToList();
+				.Concat(Assembly
-
+					.GetAssembly(typeof(ApiContainer))
-			apis.AddRange(
+					.GetTypes()
-				Assembly
+					.Where(t => typeof(IExternalApi).IsAssignableFrom(t))
-				.GetAssembly(typeof(ApiContainer))
+					.Where(t => t.IsSealed)
-				.GetTypes()
+					.Where(t => ServiceInjector.IsAvailable(serviceProvider, t)));
-				.Where(t => typeof(IExternalApi).IsAssignableFrom(t))
-				.Where(t => t.IsSealed)
-				.Where(t => ServiceInjector.IsAvailable(serviceProvider, t)));
 
 			foreach (var api in apis)
 			{

BizHawk.Client.EmuHawk/BizBox.cs

@@ -48,8 +48,7 @@ namespace BizHawk.Client.EmuHawk
 				.Select(t => t.GetCustomAttributes(false).OfType<CoreAttribute>().FirstOrDefault())
 				.Where(a => a != null)
 				.Where(a => a.Released)
-				.OrderByDescending(a => a.CoreName.ToLower())
+				.OrderByDescending(a => a.CoreName.ToLower());
-				.ToList();
 
 			foreach (var core in cores)
 			{

BizHawk.Client.EmuHawk/CustomControls/InputRoll.cs

@@ -1373,7 +1373,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					if (SelectedRows.Any() && LetKeysModifySelection && SelectedRows.First() > 0)
 					{
-						foreach (var row in SelectedRows.ToList())
+						foreach (var row in SelectedRows.ToList()) // clones SelectedRows
 						{
 							SelectRow(row - 1, true);
 							SelectRow(row, false);
@@ -1384,7 +1384,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					if (SelectedRows.Any() && LetKeysModifySelection)
 					{
-						foreach (var row in SelectedRows.Reverse().ToList())
+						foreach (var row in SelectedRows.Reverse()) // clones SelectedRows
 						{
 							SelectRow(row + 1, true);
 							SelectRow(row, false);
@@ -1695,14 +1695,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					if (toggle && _selectedItems.Any(x => x.RowIndex.HasValue && x.RowIndex == cell.RowIndex))
 					{
-						var items = _selectedItems
+						_selectedItems.RemoveWhere(x => x.RowIndex.HasValue && x.RowIndex == cell.RowIndex);
-							.Where(x => x.RowIndex.HasValue && x.RowIndex == cell.RowIndex)
-							.ToList();
-
-						foreach (var item in items)
-						{
-							_selectedItems.Remove(item);
-						}
 					}
 					else
 					{
@@ -2054,13 +2047,11 @@ namespace BizHawk.Client.EmuHawk
 			{
 				int pos = 0;
 
-				var columns = VisibleColumns.ToList();
+				foreach (var col in VisibleColumns)
-
-				for (int i = 0; i < columns.Count; i++)
 				{
-					columns[i].Left = pos;
+					col.Left = pos;
-					pos += columns[i].Width.Value;
+					pos += col.Width.Value;
-					columns[i].Right = pos;
+					col.Right = pos;
 				}
 
 				DoChangeCallback();

BizHawk.Client.EmuHawk/MainForm.Hotkey.cs

@@ -347,7 +347,10 @@ namespace BizHawk.Client.EmuHawk
 							type = " (on)";
 						}
 
-						Global.CheatList.ToList().ForEach(x => x.Toggle());
+						foreach (var x in Global.CheatList)
+						{
+							x.Toggle();
+						}
 						GlobalWin.OSD.AddMessage($"Cheats toggled{type}");
 					}
 

BizHawk.Client.EmuHawk/Sound/Output/DirectSoundSoundOutput.cs

@@ -42,7 +42,7 @@ namespace BizHawk.Client.EmuHawk
 
 		public static IEnumerable<string> GetDeviceNames()
 		{
-			return DirectSound.GetDevices().Select(d => d.Description).ToList();
+			return DirectSound.GetDevices().Select(d => d.Description);
 		}
 
 		private int BufferSizeSamples { get; set; }

BizHawk.Client.EmuHawk/Sound/Output/XAudio2SoundOutput.cs

@@ -49,7 +49,9 @@ namespace BizHawk.Client.EmuHawk
 		{
 			using (XAudio2 device = new XAudio2())
 			{
-				return Enumerable.Range(0, device.DeviceCount).Select(n => device.GetDeviceDetails(n).DisplayName).ToList();
+				return Enumerable.Range(0, device.DeviceCount)
+					.Select(n => device.GetDeviceDetails(n).DisplayName)
+					.ToList(); // enumerate before local var device is disposed
 			}
 		}
 

BizHawk.Client.EmuHawk/config/HotkeyConfig.cs

@@ -101,7 +101,7 @@ namespace BizHawk.Client.EmuHawk
 			HotkeyTabControl.TabPages.Clear();
 
 			// Buckets
-			var tabs = Global.Config.HotkeyBindings.Select(x => x.TabGroup).Distinct().ToList();
+			var tabs = Global.Config.HotkeyBindings.Select(x => x.TabGroup).Distinct();
 
 			foreach (var tab in tabs)
 			{
@@ -110,7 +110,7 @@ namespace BizHawk.Client.EmuHawk
 
 				var tb = new TabPage {Name = tab, Text = tab};
 
-				var bindings = Global.Config.HotkeyBindings.Where(x => x.TabGroup == tab).OrderBy(x => x.Ordinal).ThenBy(x => x.DisplayName).ToList();
+				var bindings = Global.Config.HotkeyBindings.Where(x => x.TabGroup == tab).OrderBy(x => x.Ordinal).ThenBy(x => x.DisplayName);
 
 				int iwOffsetX = UIHelper.ScaleX(110);
 				int iwOffsetY = UIHelper.ScaleY(-4);

BizHawk.Client.EmuHawk/config/NES/NESSyncSettingsForm.cs

@@ -64,7 +64,7 @@ namespace BizHawk.Client.EmuHawk
 				typeof(NES.NESSyncSettings.Region),
 				(string)RegionComboBox.SelectedItem);
 
-			List<byte> oldRam = _syncSettings.InitialWRamStatePattern?.ToList() ?? new List<byte>();
+			var oldRam = _syncSettings.InitialWRamStatePattern ?? new List<byte>();
 
 			if (!string.IsNullOrWhiteSpace(RamPatternOverrideBox.Text))
 			{

BizHawk.Client.EmuHawk/config/PathConfig.cs

@@ -114,8 +114,7 @@ namespace BizHawk.Client.EmuHawk
 				var paths = pathCollection
 					.Where(p => p.System == systemId)
 					.OrderBy(p => p.Ordinal)
-					.ThenBy(p => p.Type)
+					.ThenBy(p => p.Type);
-					.ToList();
 
 				var y = UIHelper.ScaleY(14);
 				foreach (var path in paths)
@@ -243,10 +242,10 @@ namespace BizHawk.Client.EmuHawk
 
 		private void DoRomToggle()
 		{
-			AllPathControls
+			foreach (var control in AllPathControls.Where(c => c.Name == "ROM"))
-				.Where(c => c.Name == "ROM")
+			{
-				.ToList()
+				control.Enabled = !RecentForROMs.Checked;
-				.ForEach(control => control.Enabled = !RecentForROMs.Checked);
+			}
 		}
 
 		private IEnumerable<TextBox> AllPathBoxes

BizHawk.Client.EmuHawk/movie/PlayMovie.cs

@@ -306,10 +306,10 @@ namespace BizHawk.Client.EmuHawk
 		{
 			var filePaths = (string[])e.Data.GetData(DataFormats.FileDrop);
 
-			filePaths
+			foreach (var path in filePaths.Where(path => MovieService.MovieExtensions.Contains(Path.GetExtension(path).Replace(".", ""))))
-				.Where(path => MovieService.MovieExtensions.Contains(Path.GetExtension(path).Replace(".", "")))
+			{
-				.ToList()
+				AddMovieToList(path, force: true);
-				.ForEach(path => AddMovieToList(path, force: true));
+			}
 
 			RefreshMovieList();
 		}
@@ -468,11 +468,11 @@ namespace BizHawk.Client.EmuHawk
 
 		private void EditMenuItem_Click(object sender, EventArgs e)
 		{
-			MovieView.SelectedIndices
+			foreach (var movie in MovieView.SelectedIndices.Cast<int>()
-				.Cast<int>()
+				.Select(index => _movieList[index]))
-				.Select(index => _movieList[index])
+			{
-				.ToList()
+				System.Diagnostics.Process.Start(movie.Filename);
-				.ForEach(movie => System.Diagnostics.Process.Start(movie.Filename));
+			}
 		}
 
 		#endregion

BizHawk.Client.EmuHawk/tools/BasicBot/BasicBot.cs

@@ -449,10 +449,10 @@ namespace BizHawk.Client.EmuHawk
 			CurrentFileName = "";
 			_bestBotAttempt = null;
 
-			ControlProbabilityPanel.Controls
+			foreach (var cp in ControlProbabilityPanel.Controls.OfType<BotControlsRow>())
-				.OfType<BotControlsRow>()
+			{
-				.ToList()
+				cp.Probability = 0;
-				.ForEach(cp => cp.Probability = 0);
+			}
 
 			FrameLength = 0;
 			MaximizeAddress = 0;

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

@@ -486,7 +486,7 @@ namespace BizHawk.Client.EmuHawk
 				Global.CheatList.Insert(index - 1, cheat);
 			}
 
-			var newindices = indices.Select(t => t - 1).ToList();
+			var newindices = indices.Select(t => t - 1);
 
 			CheatListView.SelectedIndices.Clear();
 			foreach (var newi in newindices)
@@ -515,7 +515,7 @@ namespace BizHawk.Client.EmuHawk
 
 			UpdateMessageLabel();
 
-			var newindices = indices.Select(t => t + 1).ToList();
+			var newindices = indices.Select(t => t + 1);
 
 			CheatListView.SelectedIndices.Clear();
 			foreach (var newi in newindices)
@@ -533,7 +533,10 @@ namespace BizHawk.Client.EmuHawk
 
 		private void ToggleMenuItem_Click(object sender, EventArgs e)
 		{
-			SelectedCheats.ToList().ForEach(x => x.Toggle());
+			foreach (var x in SelectedCheats)
+			{
+				x.Toggle();
+			}
 			CheatListView.Refresh();
 		}
 

BizHawk.Client.EmuHawk/tools/Debugger/RegisterBoxControl.cs

@@ -41,46 +41,37 @@ namespace BizHawk.Client.EmuHawk
 				{
 					if (Controls.OfType<Panel>().Any(p => p.Name == "FlagPanel"))
 					{
-						Controls
+						foreach (var checkbox in Controls.OfType<Panel>()
-							.OfType<Panel>()
 							.First(p => p.Name == "FlagPanel")
 							.Controls
-							.OfType<CheckBox>()
+							.OfType<CheckBox>())
-							.ToList()
+						{
-							.ForEach(checkbox =>
+							if (checkbox.Name == register.Key)
 							{
-								if (checkbox.Name == register.Key)
+								checkbox.Checked = register.Value.Value == 1;
-								{
+							}
-									checkbox.Checked = register.Value.Value == 1;
+						}
-								}
-							});
 					}
 
 					if (_canSetCpuRegisters)
 					{
-						Controls
+						foreach (var textbox in Controls.OfType<TextBox>())
-							.OfType<TextBox>()
+						{
-							.ToList()
+							if (textbox.Name == register.Key)
-							.ForEach(textbox =>
 							{
-								if (textbox.Name == register.Key)
+								textbox.Text = register.Value.Value.ToHexString(register.Value.BitSize / 4);
-								{
+							}
-									textbox.Text = register.Value.Value.ToHexString(register.Value.BitSize / 4);
+						}
-								}
-							});
 					}
 					else
 					{
-						Controls
+						foreach (var label in Controls.OfType<Label>())
-							.OfType<Label>()
+						{
-							.ToList()
+							if (label.Name == register.Key)
-							.ForEach(label =>
 							{
-								if (label.Name == register.Key)
+								label.Text = register.Value.Value.ToHexString(register.Value.BitSize / 4);
-								{
+							}
-									label.Text = register.Value.Value.ToHexString(register.Value.BitSize / 4);
+						}
-								}
-							});
 					}
 				}
 

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

@@ -213,7 +213,7 @@ namespace BizHawk.Client.EmuHawk
 				SetDomain(domain);
 				SetHighlighted(addrList[0]);
 				_secondaryHighlightedAddresses.Clear();
-				_secondaryHighlightedAddresses.AddRange(addrList.Where(addr => addr != addrList[0]).ToList());
+				_secondaryHighlightedAddresses.AddRange(addrList.Where(addr => addr != addrList[0]));
 				ClearNibbles();
 				UpdateValues();
 				MemoryViewerBox.Refresh();
@@ -835,8 +835,7 @@ namespace BizHawk.Client.EmuHawk
 			if (address >= 0) 
 			{
 				// TODO: can't unfreeze address 0??
-				Global.CheatList.RemoveRange(
+				Global.CheatList.RemoveRange(Global.CheatList.Where(x => x.Contains(address)));
-					Global.CheatList.Where(x => x.Contains(address)).ToList());
 			}
 
 			MemoryViewerBox.Refresh();

BizHawk.Client.EmuHawk/tools/Lua/Libraries/EmuLuaLibrary.Console.cs

@@ -123,8 +123,7 @@ namespace BizHawk.Client.EmuHawk
 							}
 						}
 
-						kvps = kvps.OrderBy(x => x.Key).ToList();
+						foreach (var kvp in kvps.OrderBy(x => x.Key))
-						foreach (var kvp in kvps)
 						{
 							sb
 								.Append("\"")

BizHawk.Client.EmuHawk/tools/Lua/Libraries/EmuLuaLibrary.Forms.cs

@@ -149,11 +149,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					if (control.Handle == ptr)
 					{
-						var luaEvents = form.ControlEvents.Where(x => x.Control == ptr).ToList();
+						form.ControlEvents.RemoveAll(x => x.Control == ptr);
-						foreach (var luaEvent in luaEvents)
-						{
-							form.ControlEvents.Remove(luaEvent);
-						}
 					}
 				}
 			}

BizHawk.Client.EmuHawk/tools/Lua/Libraries/EmuLuaLibrary.cs

@@ -35,15 +35,12 @@ namespace BizHawk.Client.EmuHawk
 				.Where(t => typeof(LuaLibraryBase).IsAssignableFrom(t))
 				.Where(t => t.IsSealed)
 				.Where(t => ServiceInjector.IsAvailable(serviceProvider, t))
-				.ToList();
+				.Concat(Assembly
-
+					.GetAssembly(typeof(EmuLuaLibrary))
-			libs.AddRange(
+					.GetTypes()
-				Assembly
+					.Where(t => typeof(LuaLibraryBase).IsAssignableFrom(t))
-				.GetAssembly(typeof(EmuLuaLibrary))
+					.Where(t => t.IsSealed)
-				.GetTypes()
+					.Where(t => ServiceInjector.IsAvailable(serviceProvider, t)));
-				.Where(t => typeof(LuaLibraryBase).IsAssignableFrom(t))
-				.Where(t => t.IsSealed)
-				.Where(t => ServiceInjector.IsAvailable(serviceProvider, t)));
 
 			foreach (var lib in libs)
 			{

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

@@ -171,14 +171,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					LuaImp.CallExitEvent(file);
 
-					var functions = LuaImp.GetRegisteredFunctions()
+					LuaImp.GetRegisteredFunctions().RemoveAll(lf => lf.Lua == file.Thread);
-						.Where(lf => lf.Lua == file.Thread)
-						.ToList();
-
-					foreach (var function in functions)
-					{
-						LuaImp.GetRegisteredFunctions().Remove(function);
-					}
 
 					UpdateRegisteredFunctionsDialog();
 
@@ -692,7 +685,7 @@ namespace BizHawk.Client.EmuHawk
 
 		private static void UpdateRegisteredFunctionsDialog()
 		{
-			foreach (var form in Application.OpenForms.OfType<LuaRegisteredFunctionsList>().ToList())
+			foreach (var form in Application.OpenForms.OfType<LuaRegisteredFunctionsList>())
 			{
 				form.UpdateValues();
 			}
@@ -850,16 +843,10 @@ namespace BizHawk.Client.EmuHawk
 				{
 					LuaImp.CallExitEvent(file);
 
-					var items = SelectedItems.ToList();
+					foreach (var selectedItem in SelectedItems)
-					foreach (var selectedItem in items)
 					{
 						var temp = selectedItem;
-						var functions = LuaImp.GetRegisteredFunctions().Where(lf => lf.Lua == temp.Thread).ToList();
+						LuaImp.GetRegisteredFunctions().RemoveAll(lf => lf.Lua == temp.Thread);
-						foreach (var function in functions)
-						{
-							LuaImp.GetRegisteredFunctions().Remove(function);
-						}
-
 						UpdateRegisteredFunctionsDialog();
 					}
 
@@ -913,7 +900,10 @@ namespace BizHawk.Client.EmuHawk
 
 		private void PauseScriptMenuItem_Click(object sender, EventArgs e)
 		{
-			SelectedFiles.ToList().ForEach(x => x.TogglePause());
+			foreach (var x in SelectedFiles)
+			{
+				x.TogglePause();
+			}
 			UpdateDialog();
 		}
 
@@ -926,14 +916,14 @@ namespace BizHawk.Client.EmuHawk
 
 		private void EditScriptMenuItem_Click(object sender, EventArgs e)
 		{
-			SelectedFiles.ToList().ForEach(file =>
+			foreach (var file in SelectedFiles)
 			{
 				Process.Start(new ProcessStartInfo
 				{
 					Verb = "Open",
 					FileName = ProcessPath(file.Path)
 				});
-			});
+			}
 		}
 
 		private void RemoveScriptMenuItem_Click(object sender, EventArgs e)
@@ -944,11 +934,7 @@ namespace BizHawk.Client.EmuHawk
 				foreach (var item in items)
 				{
 					var temp = item;
-					var functions = LuaImp.GetRegisteredFunctions().Where(x => x.Lua == temp.Thread).ToList();
+					LuaImp.GetRegisteredFunctions().RemoveAll(x => x.Lua == temp.Thread);
-					foreach (var function in functions)
-					{
-						LuaImp.GetRegisteredFunctions().Remove(function);
-					}
 
 					LuaImp.ScriptList.Remove(item);
 				}
@@ -1018,7 +1004,7 @@ namespace BizHawk.Client.EmuHawk
 				LuaImp.ScriptList.Insert(index - 1, file);
 			}
 
-			var newIndices = indices.Select(t => t - 1).ToList();
+			var newIndices = indices.Select(t => t - 1);
 
 			LuaListView.SelectedIndices.Clear();
 			foreach (var i in newIndices)
@@ -1044,7 +1030,7 @@ namespace BizHawk.Client.EmuHawk
 				LuaImp.ScriptList.Insert(indices[i] + 1, file);
 			}
 
-			var newIndices = indices.Select(t => t + 1).ToList();
+			var newIndices = indices.Select(t => t + 1);
 
 			LuaListView.SelectedIndices.Clear();
 			foreach (var i in newIndices)

BizHawk.Client.EmuHawk/tools/Lua/LuaRegisteredFunctionsList.cs

@@ -46,7 +46,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			FunctionView.Items.Clear();
 			
-			var nlfs = GlobalWin.Tools.LuaConsole.LuaImp.GetRegisteredFunctions().OrderBy(x => x.Event).ThenBy(x => x.Name).ToList();
+			var nlfs = GlobalWin.Tools.LuaConsole.LuaImp.GetRegisteredFunctions().OrderBy(x => x.Event).ThenBy(x => x.Name);
 			foreach (var nlf in nlfs)
 			{
 				var item = new ListViewItem { Text = nlf.Event };

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

@@ -186,9 +186,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			try
 			{
-				var fileSelectors = FileSelectors.ToList();
+				var names = FileSelectors.Select(f => f.GetName());
-
-				var names = fileSelectors.Select(f => f.GetName());
 
 				var name = NameBox.Text;
 

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

@@ -677,13 +677,12 @@ namespace BizHawk.Client.EmuHawk
 			if (TasView.AnyRowsSelected)
 			{
 				var wasPaused = Mainform.EmulatorPaused;
-				var framesToInsert = TasView.SelectedRows.ToList();
+				var framesToInsert = TasView.SelectedRows;
 				var insertionFrame = Math.Min(TasView.LastSelectedIndex.Value + 1, CurrentTasMovie.InputLogLength);
 				var needsToRollback = TasView.FirstSelectedIndex < Emulator.Frame;
 
 				var inputLog = framesToInsert
-					.Select(frame => CurrentTasMovie.GetInputLogEntry(frame))
+					.Select(frame => CurrentTasMovie.GetInputLogEntry(frame));
-					.ToList();
 
 				CurrentTasMovie.InsertInput(insertionFrame, inputLog);
 
@@ -780,11 +779,7 @@ namespace BizHawk.Client.EmuHawk
 
 		private void RemoveMarkersMenuItem_Click(object sender, EventArgs e)
 		{
-			IEnumerable<TasMovieMarker> markers = CurrentTasMovie.Markers.Where(m => TasView.SelectedRows.Contains(m.Frame));
+			CurrentTasMovie.Markers.RemoveAll(m => TasView.SelectedRows.Contains(m.Frame));
-			foreach (TasMovieMarker m in markers.ToList())
-			{
-				CurrentTasMovie.Markers.Remove(m);
-			}
 			MarkerControl.ShrinkSelection();
 			RefreshDialog();
 		}

BizHawk.Client.EmuHawk/tools/VirtualPads/VirtualPad.cs

@@ -136,10 +136,10 @@ namespace BizHawk.Client.EmuHawk
 
 		public void ClearBoolean()
 		{
-			PadControls
+			foreach (var p in PadControls.OfType<VirtualPadButton>())
-				.OfType<VirtualPadButton>()
+			{
-				.ToList()
+				p.Clear();
-				.ForEach(p => p.Clear());
+			}
 		}
 
 		public void Set(IController controller)
@@ -149,28 +149,28 @@ namespace BizHawk.Client.EmuHawk
 
 		public void SetPrevious(IController previous)
 		{
-			PadControls
+			foreach (var c in PadControls.OfType<VirtualPadAnalogStick>())
-				.OfType<VirtualPadAnalogStick>()
+			{
-				.ToList()
+				c.SetPrevious(previous);
-				.ForEach(c => c.SetPrevious(previous));
+			}
 		}
 
 		public void BumpAnalog(int? x, int? y)
 		{
-			PadControls
+			foreach (var a in PadControls.OfType<VirtualPadAnalogStick>())
-				.OfType<VirtualPadAnalogStick>()
+			{
-				.ToList()
+				a.Bump(x, y);
-				.ForEach(a => a.Bump(x, y));
+			}
 
-			PadControls
+			foreach (var a in PadControls.OfType<VirtualPadAnalogButton>())
-				.OfType<VirtualPadAnalogButton>()
+			{
-				.ToList()
+				a.Bump(x);
-				.ForEach(a => a.Bump(x));
+			}
 
-			PadControls
+			foreach (var a in PadControls.OfType<VirtualPadTargetScreen>())
-				.OfType<VirtualPadTargetScreen>()
+			{
-				.ToList()
+				a.Bump(x, y);
-				.ForEach(a => a.Bump(x, y));
+			}
 		}
 	}
 }

BizHawk.Client.EmuHawk/tools/Watch/RamSearch.cs

@@ -875,7 +875,7 @@ namespace BizHawk.Client.EmuHawk
 					InitialLocation = this.ChildPointToScreen(WatchListView)
 				};
 
-				poke.SetWatch(SelectedIndices.Select(t => _searches[t]).ToList());
+				poke.SetWatch(SelectedIndices.Select(t => _searches[t]));
 				poke.ShowHawkDialog();
 
 				UpdateList();

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

@@ -898,7 +898,7 @@ namespace BizHawk.Client.EmuHawk
 
 			Changes();
 
-			var indices = indexes.Select(t => t - 1).ToList();
+			var indices = indexes.Select(t => t - 1);
 
 			WatchListView.SelectedIndices.Clear();
 			foreach (var t in indices)
@@ -924,7 +924,7 @@ namespace BizHawk.Client.EmuHawk
 				_watches.Insert(indices[i] + 1, watch);
 			}
 
-			var newIndices = indices.Select(t => t + 1).ToList();
+			var newIndices = indices.Select(t => t + 1);
 
 			WatchListView.SelectedIndices.Clear();
 			foreach (var t in newIndices)
@@ -1284,7 +1284,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			var items = _watches
 				.Where(watch => watch.Address >= watch.Domain.Size)
-				.ToList();
+				.ToList(); // enumerate because _watches is about to be changed
 
 			foreach (var item in items)
 			{

BizHawk.Client.MultiHawk/Mainform.cs

@@ -93,7 +93,7 @@ namespace BizHawk.Client.MultiHawk
 			{
 				Global.MovieSession.Movie.Stop();
 
-				foreach (var ew in EmulatorWindows.ToList())
+				foreach (var ew in EmulatorWindows)
 				{
 					ew.ShutDown();
 				}
@@ -1421,7 +1421,7 @@ namespace BizHawk.Client.MultiHawk
 
 		private void CloseAllWindows()
 		{
-			foreach (var ew in EmulatorWindows.ToList())
+			foreach (var ew in EmulatorWindows)
 			{
 				ew.Close();
 			}
@@ -1431,7 +1431,7 @@ namespace BizHawk.Client.MultiHawk
 
 		private void NewSessionMenuItem_Click(object sender, EventArgs e)
 		{
-			foreach (var ew in EmulatorWindows.ToList())
+			foreach (var ew in EmulatorWindows)
 			{
 				ew.Close();
 			}

BizHawk.Client.MultiHawk/movie/PlayMovie.cs

@@ -300,10 +300,10 @@ namespace BizHawk.Client.MultiHawk
 		{
 			var filePaths = (string[])e.Data.GetData(DataFormats.FileDrop);
 
-			filePaths
+			foreach (var path in filePaths.Where(path => MovieService.MovieExtensions.Contains(Path.GetExtension(path).Replace(".", ""))))
-				.Where(path => MovieService.MovieExtensions.Contains(Path.GetExtension(path).Replace(".", "")))
+			{
-				.ToList()
+				AddMovieToList(path, force: true);
-				.ForEach(path => AddMovieToList(path, force: true));
+			}
 
 			RefreshMovieList();
 		}
@@ -457,11 +457,11 @@ namespace BizHawk.Client.MultiHawk
 
 		private void EditMenuItem_Click(object sender, EventArgs e)
 		{
-			MovieView.SelectedIndices
+			foreach (var movie in MovieView.SelectedIndices.Cast<int>()
-				.Cast<int>()
+				.Select(index => _movieList[index]))
-				.Select(index => _movieList[index])
+			{
-				.ToList()
+				System.Diagnostics.Process.Start(movie.Filename);
-				.ForEach(movie => System.Diagnostics.Process.Start(movie.Filename));
+			}
 		}
 
 		#endregion

BizHawk.Common/BizInvoke/BizExvoker.cs

@@ -64,8 +64,7 @@ namespace BizHawk.Common.BizInvoke
 					Info = m,
 					Attr = m.GetCustomAttributes(true).OfType<BizExportAttribute>().FirstOrDefault()
 				})
-				.Where(a => a.Attr != null)
+				.Where(a => a.Attr != null);
-				.ToList();
 
 				var typeBuilder = ImplModuleBuilder.DefineType($"Bizhawk.BizExvokeHolder{type.Name}", TypeAttributes.Class | TypeAttributes.Public | TypeAttributes.Sealed);
 

BizHawk.Emulation.Common/ServiceAttributes.cs

@@ -25,7 +25,7 @@ namespace BizHawk.Emulation.Common
 	{
 		public ServiceNotApplicableAttribute(params Type[] types)
 		{
-			NotApplicableTypes = types?.ToList() ?? new List<Type>();
+			NotApplicableTypes = types?.AsEnumerable() ?? Enumerable.Empty<Type>();
 		}
 
 		public IEnumerable<Type> NotApplicableTypes { get; private set; }

BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/Display/AmstradGateArray.cs

@@ -1035,8 +1035,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
         public int[] GetVideoBuffer()
         {
             // get only lines that have pixel data
-            var lines = ScreenLines.Where(a => a.Pixels.Count > 0).ToList();
+            var lines = ScreenLines.Where(a => a.Pixels.Count > 0);
-            var height = lines.Count();
 
             int pos = 0;
             int lCount = 0;

BizHawk.Emulation.Cores/Computers/AmstradCPC/Media/Tape/TapeDataBlock.cs

@@ -152,12 +152,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
         /// </summary>
         public void SetDataPeriodsArray(int[] periodArray)
         {
-            DataPeriods = new List<int>();
+            DataPeriods = periodArray?.ToList() ?? new List<int>();
-
-            if (periodArray == null)
-                return;
-
-            DataPeriods = periodArray.ToList();
         }
 
         /// <summary>

BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Disk/IPFFormat/IPFFloppyDisk.cs

@@ -65,7 +65,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             // now process the blocks
             var infoBlock = blocks.Where(a => a.RecordType == RecordHeaderType.INFO).FirstOrDefault();
             var IMGEblocks = blocks.Where(a => a.RecordType == RecordHeaderType.IMGE).ToList();
-            var DATAblocks = blocks.Where(a => a.RecordType == RecordHeaderType.DATA).ToList();
+            var DATAblocks = blocks.Where(a => a.RecordType == RecordHeaderType.DATA);
 
             DiskHeader.NumberOfTracks = (byte)(IMGEblocks.Count());
             DiskHeader.NumberOfSides = (byte)(infoBlock.INFOmaxSide + 1);

BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/TapeDataBlock.cs

@@ -153,12 +153,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
         /// </summary>
         public void SetDataPeriodsArray(int[] periodArray)
         {
-            DataPeriods = new List<int>();
+            DataPeriods = periodArray?.ToList() ?? new List<int>();
-
-            if (periodArray == null)
-                return;
-
-            DataPeriods = periodArray.ToList();
         }
 
         /// <summary>

BizHawk.Emulation.Cores/Consoles/Atari/2600/Atari2600.cs

@@ -75,7 +75,7 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 			{
 				Name = _game.Name,
 				System = "A26",
-				MetaData = "m=" + _mapper.GetType().ToString().Split('.').ToList().Last(),
+				MetaData = "m=" + _mapper.GetType().ToString().Split('.').Last(),
 				Hash = Rom.HashSHA1(),
 				Region = _game.Region,
 				Status = RomStatus.Unknown

BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/GambatteLink.IDebuggable.cs

@@ -16,7 +16,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.Gameboy
 			var right = R.GetCpuFlagsAndRegisters()
 				.Select(reg => new KeyValuePair<string, RegisterValue>("Right " + reg.Key, reg.Value));
 
-			return left.Union(right).ToList().ToDictionary(pair => pair.Key, pair => pair.Value);
+			return left.Union(right).ToDictionary(pair => pair.Key, pair => pair.Value);
 		}
 
 		public void SetCpuRegister(string register, int value)

BizHawk.Emulation.Cores/CoreInventory.cs

@@ -165,7 +165,7 @@ namespace BizHawk.Emulation.Cores
 						if (coreattr.Length != 1)
 							throw new InvalidOperationException($"{nameof(IEmulator)} {typ} without {nameof(CoreAttribute)}s!");
 						var cons = typ.GetConstructors(BindingFlags.Public | BindingFlags.Instance)
-							.Where(c => c.GetCustomAttributes(typeof(CoreConstructorAttribute), false).Length > 0).ToList();
+							.Where(c => c.GetCustomAttributes(typeof(CoreConstructorAttribute), false).Length > 0);
 						foreach(var con in cons)
 						{
 							foreach (string system in ((CoreConstructorAttribute)con.GetCustomAttributes(typeof(CoreConstructorAttribute), false)[0]).Systems)

BizHawk.Emulation.Cores/Waterbox/ElfRunner.cs

@@ -253,17 +253,15 @@ namespace BizHawk.Emulation.Cores.Waterbox
 
 		private void RegisterSymbols()
 		{
-			var symbols = ((ISymbolTable)_elf.GetSection(".symtab"))
+			_symlist = ((ISymbolTable) _elf.GetSection(".symtab")).Entries
-			.Entries
+				.Cast<SymbolEntry<long>>()
-			.Cast<SymbolEntry<long>>();
+				.ToList();
 
 			// when there are duplicate names, don't register either in the dictionary
-			_symdict = symbols
+			_symdict = _symlist
-			.GroupBy(e => e.Name)
+				.GroupBy(e => e.Name)
-			.Where(g => g.Count() == 1)
+				.Where(g => g.Count() == 1)
-			.ToDictionary(g => g.Key, g => g.First());
+				.ToDictionary(g => g.Key, g => g.First());
-
-			_symlist = symbols.ToList();
 		}
 
 		public void Seal()

BizHawk.Emulation.DiscSystem/CDFS/ISOFile.cs

@@ -182,9 +182,7 @@ namespace BizHawk.Emulation.DiscSystem
                 return fileNodes;
 
             // get all folders
-            List<KeyValuePair<string, ISONode>> dirs = (from a in Root.Children
+            var dirs = (from a in Root.Children where a.Value.GetType() == typeof(ISODirectoryNode) select a);
-                                                       where a.Value.GetType() == typeof(ISODirectoryNode)
-                                                        select a).ToList();
             // iterate through each folder
             foreach (var d in dirs)
             {