Replace empty string with constant

docs/Changes.txt

@@ -9,6 +9,10 @@ x: Bugfix
 
 =========================================
 
+0.5.1.0 (2023-12-06)
+* Moved to .NET 8.0
+* Use string.Empty for empty strings
+
 0.5.0.0 (2021-12-04)
 * Moved to .NET 6.0
 * Switched to deterministic versioning

src/MixAssembler/Parser.cs

@@ -145,11 +145,11 @@ private static ParsedSourceLine ParseLine(string sourceLine, ParsingStatus statu
 			lineFields[OpFieldIndex] = lineFields[OpFieldIndex].ToUpper();
 			lineFields[AddressFieldIndex] = lineFields[AddressFieldIndex].ToUpper();
 
-			if (lineFields[OpFieldIndex] == "")
+			if (lineFields[OpFieldIndex] == string.Empty)
 			{
 				status.ReportParsingError(LineSection.LocationField, 0, sourceLine.Length, "op and address fields are missing");
 
-				return new ParsedSourceLine(status.LineNumber, lineFields[0], "", "", "", null, null);
+				return new ParsedSourceLine(status.LineNumber, lineFields[0], string.Empty, string.Empty, string.Empty, null, null);
 			}
 
 			var symbol = ParseLocField(lineFields[LocFieldIndex], status);
@@ -170,7 +170,7 @@ private static ParsedSourceLine ParseLine(string sourceLine, ParsingStatus statu
 
 		private static SymbolBase ParseLocField(string locField, ParsingStatus status)
 		{
-			if (locField == "")
+			if (locField == string.Empty)
 				return null;
 
 			status.LineSection = LineSection.LocationField;
@@ -249,23 +249,23 @@ private static string[] SplitLine(string sourceLine)
 			var searchBeyondIndex = FindFirstWhiteSpace(sourceLine, -1);
 
 			if (searchBeyondIndex == -1)
-				return new string[] { sourceLine, "", "", "" };
+				return new string[] { sourceLine, string.Empty, string.Empty, string.Empty };
 
 			var opFieldStart = FindFirstNonWhiteSpace(sourceLine, searchBeyondIndex);
 
 			if (opFieldStart == -1)
-				return new string[] { sourceLine.Substring(0, searchBeyondIndex), "", "", "" };
+				return new string[] { sourceLine.Substring(0, searchBeyondIndex), string.Empty, string.Empty, string.Empty };
 
 			var opFieldEnd = FindFirstWhiteSpace(sourceLine, opFieldStart);
 
 			if (opFieldEnd == -1)
-				return new string[] { sourceLine.Substring(0, searchBeyondIndex), sourceLine[opFieldStart..], "", "" };
+				return new string[] { sourceLine.Substring(0, searchBeyondIndex), sourceLine[opFieldStart..], string.Empty, string.Empty };
 
 			int opFieldLength = opFieldEnd - opFieldStart;
 			var addressFieldStart = FindFirstNonWhiteSpace(sourceLine, opFieldEnd);
 
 			if (addressFieldStart == -1)
-				return new string[] { sourceLine.Substring(0, searchBeyondIndex), sourceLine.Substring(opFieldStart, opFieldLength), "", "" };
+				return new string[] { sourceLine.Substring(0, searchBeyondIndex), sourceLine.Substring(opFieldStart, opFieldLength), string.Empty, string.Empty };
 
 			if (sourceLine[addressFieldStart] == '"')
 			{
@@ -280,13 +280,13 @@ private static string[] SplitLine(string sourceLine)
 				addressFieldEnd = FindFirstWhiteSpace(sourceLine, addressFieldStart);
 
 			if (addressFieldEnd == -1)
-				return new string[] { sourceLine.Substring(0, searchBeyondIndex), sourceLine.Substring(opFieldStart, opFieldLength), sourceLine[addressFieldStart..], "" };
+				return new string[] { sourceLine.Substring(0, searchBeyondIndex), sourceLine.Substring(opFieldStart, opFieldLength), sourceLine[addressFieldStart..], string.Empty };
 
 			int addressFieldLength = addressFieldEnd - addressFieldStart;
 			var commentFieldStart = FindFirstNonWhiteSpace(sourceLine, addressFieldEnd);
 
 			if (commentFieldStart == -1)
-				return new string[] { sourceLine.Substring(0, searchBeyondIndex), sourceLine.Substring(opFieldStart, opFieldLength), sourceLine.Substring(addressFieldStart, addressFieldLength), "" };
+				return new string[] { sourceLine.Substring(0, searchBeyondIndex), sourceLine.Substring(opFieldStart, opFieldLength), sourceLine.Substring(addressFieldStart, addressFieldLength), string.Empty };
 
 			return new string[] { sourceLine.Substring(0, searchBeyondIndex), sourceLine.Substring(opFieldStart, opFieldLength), sourceLine.Substring(addressFieldStart, addressFieldLength), sourceLine[commentFieldStart..] };
 		}

src/MixAssembler/Symbol/LiteralConstantSymbol.cs

@@ -45,7 +45,7 @@ public override bool IsValueDefined(int currentAddress)
 			=> this.valueDefined;
 
 		private static string GetName(Word.Signs literalSign, long literalMagnitude, int count)
-			=> string.Concat("=", literalSign.IsNegative() ? "-" : "", literalMagnitude, '=', count);
+			=> string.Concat("=", literalSign.IsNegative() ? "-" : string.Empty, literalMagnitude, '=', count);
 
 		public static IValue ParseValue(string text, int sectionCharIndex, ParsingStatus status)
 		{

src/MixEmul/Components/AssemblyFindingListView.cs

@@ -53,7 +53,7 @@ private void SelectedIndexChanged(object sender, EventArgs e)
 
 		private void AddFinding(AssemblyFinding finding)
 		{
-			var item = new ListViewItem(new string[] { finding.Severity.ToString(), (finding.LineNumber == int.MinValue) ? "" : (finding.LineNumber + 1).ToString(), finding.Message }, (int)finding.Severity)
+			var item = new ListViewItem(new string[] { finding.Severity.ToString(), (finding.LineNumber == int.MinValue) ? string.Empty : (finding.LineNumber + 1).ToString(), finding.Message }, (int)finding.Severity)
 			{
 				Tag = finding
 			};

src/MixEmul/Components/DeviceStatusControl.cs

@@ -48,7 +48,7 @@ public DeviceStatusControl(MixDevice device)
 			this.statusLabel.Name = "mStatusLabel";
 			this.statusLabel.Size = new Size(32, 16);
 			this.statusLabel.TabIndex = 1;
-			this.statusLabel.Text = "";
+			this.statusLabel.Text = string.Empty;
 			this.statusLabel.TextAlign = ContentAlignment.MiddleCenter;
 			this.statusLabel.DoubleClick += Control_DoubleClick;
 
@@ -89,9 +89,9 @@ private void ResetMenuItem_Click(object sender, EventArgs e)
 			{
 				SuspendLayout();
 
-				this.indexLabel.Text = "";
+				this.indexLabel.Text = string.Empty;
 				this.statusLabel.BackColor = Color.Gray;
-				this.statusLabel.Text = "";
+				this.statusLabel.Text = string.Empty;
 				ToolTip?.SetToolTip(this.statusLabel, "No device connected");
 
 				this.inputMenuItem.Checked = false;

src/MixEmul/Components/InstructionInstanceTextBox.cs

@@ -132,7 +132,7 @@ private void ShowAddressMenuItem_Click(object sender, EventArgs e)
 
 		private void AddTextElement(string element, bool markAsError)
 		{
-			if (element == "")
+			if (element == string.Empty)
 				return;
 
 			int textLength = TextLength;
@@ -143,12 +143,12 @@ private void AddTextElement(string element, bool markAsError)
 
 		private string GetAssemblyErrorsCaption(ParsedSourceLine line, AssemblyFindingCollection findings)
 		{
-			string caption = "";
+			string caption = string.Empty;
 			int findingNumber = 1;
 
 			foreach (AssemblyFinding finding in findings)
 			{
-				string fieldLabel = "";
+				string fieldLabel = string.Empty;
 
 				if (finding.Severity == Severity.Error)
 				{
@@ -249,7 +249,7 @@ private bool CheckContentsEditable()
 			if (ReadOnly || !this.noInstructionRendered && !this.instructionWord.IsEmpty)
 				return true;
 
-			base.Text = "";
+			base.Text = string.Empty;
 			SetEditMode();
 
 			return false;
@@ -438,7 +438,7 @@ private void HandleNoInstruction(string caption)
 			var text = new InstructionText(instance);
 
 			SuspendLayout();
-			base.Text = "";
+			base.Text = string.Empty;
 
 			ForeColor = this.lastRenderedSourceLine != null ? this.loadedInstructionTextColor : this.renderedTextColor;
 			AddTextElement(text.Mnemonic + " ", false);

src/MixEmul/Components/LogListView.cs

@@ -73,7 +73,14 @@ public LogListView()
 		}
 
 		public void AddLogLine(LogLine line)
-			=> this.listView.Items.Insert(0, new ListViewItem(new string[] { line.Severity.ToString(), line.ModuleName ?? "", (line.Address == -1) ? "" : line.Address.ToString("D4"), line.Title ?? "", line.Message ?? "" }, (int)line.Severity));
+			=> this.listView.Items.Insert(0, new ListViewItem(new string[] 
+			{ 
+				line.Severity.ToString(), 
+				line.ModuleName ?? string.Empty, 
+				(line.Address == -1) ? string.Empty : line.Address.ToString("D4"), 
+				line.Title ?? string.Empty, 
+				line.Message ?? string.Empty 
+			}, (int)line.Severity));
 
 		protected virtual void OnAddressSelected(AddressSelectedEventArgs args)
 			=> AddressSelected?.Invoke(this, args);
@@ -122,7 +129,7 @@ public int SelectedAddress
 			{
 				ListView.SelectedListViewItemCollection selectedItems = this.listView.SelectedItems;
 
-				if (selectedItems.Count == 0 || selectedItems[0].SubItems[AddressFieldIndex].Text == "")
+				if (selectedItems.Count == 0 || selectedItems[0].SubItems[AddressFieldIndex].Text == string.Empty)
 					return NoAddress;
 
 				int address = NoAddress;

src/MixEmul/Components/LongValueTextBox.cs

@@ -73,7 +73,7 @@ private void This_Leave(object sender, EventArgs e)
 		private void LongValueTextBox_Enter(object sender, EventArgs e)
 		{
 			if (ClearZero && this.magnitude == 0 && this.sign.IsPositive())
-				base.Text = "";
+				base.Text = string.Empty;
 		}
 
 		private void This_KeyDown(object sender, KeyEventArgs e)
@@ -122,7 +122,7 @@ private void CheckAndUpdateValue(string newValue)
 				long magnitude = 0;
 				Word.Signs sign = Word.Signs.Positive;
 
-				if (newValue == "" || newValue == "-")
+				if (newValue == string.Empty || newValue == "-")
 				{
 					if (MinValue > 0)
 						magnitude = MinValue;
@@ -311,7 +311,7 @@ private void This_TextChanged(object sender, EventArgs e)
 			try
 			{
 				string text = Text;
-				if (text != "" && (!SupportSign || text != "-"))
+				if (text != string.Empty && (!SupportSign || text != "-"))
 				{
 					var num = long.Parse(text);
 					textIsValid = ((num >= MinValue) && (num <= MaxValue)) && (SupportSign || (num >= 0L));

src/MixEmul/Components/MixByteCollectionCharTextBox.cs

@@ -140,7 +140,7 @@ private void This_TextChanged(object sender, EventArgs e)
 			if (this.updating)
 				return;
 
-			string validText = "";
+			string validText = string.Empty;
 
 			foreach (var c in Text.Where(c => MixByte.MixChars.Contains(c)))
 				validText += c;

src/MixEmul/Components/MixByteTextBox.cs

@@ -99,7 +99,7 @@ private void CheckAndUpdateValue(string newValue)
 		{
 			try
 			{
-				CheckAndUpdateValue(newValue == "" ? (byte)0 : byte.Parse(newValue));
+				CheckAndUpdateValue(newValue == string.Empty ? (byte)0 : byte.Parse(newValue));
 			}
 			catch (FormatException) { }
 		}
@@ -137,7 +137,7 @@ private void This_TextChanged(object sender, EventArgs e)
 			{
 				string text = Text;
 
-				if (text != "")
+				if (text != string.Empty)
 				{
 					var byteValue = byte.Parse(text);
 					textIsValid = byteValue >= 0 && byteValue <= MixByte.MaxValue;

src/MixEmul/Components/PreferencesForm.cs

@@ -1203,7 +1203,7 @@ private void UpdateDeviceFileControls(DeviceFileComboBoxItem item)
 		{
 			if (item == null)
 			{
-				this.deviceFileBox.Text = "";
+				this.deviceFileBox.Text = string.Empty;
 				this.deviceFileSetButton.Enabled = false;
 				this.deviceFileDefaultButton.Enabled = false;
 			}

src/MixEmul/Components/RegistersEditor.cs

@@ -211,7 +211,7 @@ public RegistersEditor(MixLib.Registers registers = null)
 			this.compareButton.Size = new Size(18, 21);
 			this.compareButton.Location = new Point((this.rAEditor.Left + this.rAEditor.Width) - this.compareButton.Width, this.rJEditor.Top);
 			this.compareButton.TabIndex = 21;
-			this.compareButton.Text = "" + this.registers.CompareIndicator.ToChar();
+			this.compareButton.Text = this.registers.CompareIndicator.ToChar().ToString();
 			this.compareButton.Click += CompareButton_Click;
 
 			this.overflowLabel.Location = new Point(Math.Min(this.compareButton.Left, this.overflowBox.Left) - Math.Max(this.compareLabel.Width, this.overflowLabel.Width), this.overflowBox.Top);
@@ -273,15 +273,15 @@ private void CompareButton_Click(object sender, EventArgs e)
 		{
 			var compValue = this.registers.CompareIndicator.Next();
 			this.registers.CompareIndicator = compValue;
-			this.compareButton.Text = "" + compValue.ToChar();
+			this.compareButton.Text = compValue.ToChar().ToString();
 		}
 
 		public new void Update()
 		{
 			foreach (WordValueEditor editor in this.editors)
 				editor.Update();
 
-			this.compareButton.Text = "" + this.registers.CompareIndicator.ToChar();
+			this.compareButton.Text = this.registers.CompareIndicator.ToChar().ToString();
 			this.overflowBox.Checked = this.registers.OverflowIndicator;
 
 			base.Update();

src/MixEmul/Components/SearchDialog.cs

@@ -79,7 +79,7 @@ private void FillControls()
 			}
 			else
 			{
-				this.searchTextBox.Text = "";
+				this.searchTextBox.Text = string.Empty;
 				this.valueCheckBox.Checked = true;
 				this.charsCheckBox.Checked = true;
 				this.instructionCheckBox.Checked = true;

src/MixEmul/Components/SourceCodeControl.cs

@@ -44,7 +44,7 @@ public SourceCodeControl()
 			this.sourceBox.ReadOnly = true;
 			this.sourceBox.Size = Size;
 			this.sourceBox.TabIndex = 0;
-			this.sourceBox.Text = "";
+			this.sourceBox.Text = string.Empty;
 			this.sourceBox.DetectUrls = false;
 
 			Controls.Add(this.sourceBox);
@@ -279,7 +279,7 @@ public PreInstruction[] Instructions
 			set
 			{
 				this.markedFinding = null;
-				this.sourceBox.Text = "";
+				this.sourceBox.Text = string.Empty;
 				this.instructions.Clear();
 				this.findingsColored = false;
 
@@ -306,7 +306,7 @@ public PreInstruction[] Instructions
 				{
 					while (parsedLine.LineNumber > this.instructions.Count)
 					{
-						AddLine(new ParsedSourceLine(this.instructions.Count, ""));
+						AddLine(new ParsedSourceLine(this.instructions.Count, string.Empty));
 					}
 
 					AddLine(parsedLine);
@@ -352,7 +352,7 @@ public ProcessedSourceLine(ParsedSourceLine sourceLine, int lineTextIndex)
 					!SourceLine.IsCommentLine ? AddressTextIndex + AddressTextLength + Parser.FieldSpacing : LineTextIndex;
 
 			public int LineTextLength =>
-					(SourceLine.Comment == "" ? AddressTextIndex + AddressTextLength : CommentTextIndex + SourceLine.Comment.Length) - LineTextIndex;
+					(SourceLine.Comment == string.Empty ? AddressTextIndex + AddressTextLength : CommentTextIndex + SourceLine.Comment.Length) - LineTextIndex;
 
 			public int LocTextIndex 
 				=> LineTextIndex;
@@ -376,7 +376,7 @@ public int AddressTextLength
 					if (SourceLine.IsCommentLine)
 						return 0;
 
-					if (SourceLine.Comment != "")
+					if (SourceLine.Comment != string.Empty)
 						return Math.Max(Parser.MinAddressLength, SourceLine.AddressField.Length);
 
 					return SourceLine.AddressField.Length;

src/MixEmul/Components/SymbolListView.cs

@@ -83,8 +83,8 @@ public SymbolCollection Symbols
 
 				this.listView.BeginUpdate();
 				this.listView.Items.Clear();
-				this.symbolNameTextBox.Text = "";
-				this.symbolValueTextBox.Text = "";
+				this.symbolNameTextBox.Text = string.Empty;
+				this.symbolValueTextBox.Text = string.Empty;
 
 				if (this.symbols != null)
 				{

src/MixEmul/Components/TeletypeForm.cs

@@ -233,7 +233,7 @@ public void ClearOutput()
 				return;
 			}
 
-			this.outputTextBox.Text = "";
+			this.outputTextBox.Text = string.Empty;
 		}
 
 		private void MOnTopCheckBox_CheckedChanged(object sender, EventArgs e) => TopMost = this.onTopCheckBox.Checked;
@@ -247,7 +247,7 @@ private void OutputAdded(object sender, EventArgs e)
 			}
 
 			string outputLine;
-			string textToAdd = "";
+			string textToAdd = string.Empty;
 
 			while ((outputLine = this.teletypeDevice.GetOutputLine()) != null)
 			{
@@ -276,7 +276,7 @@ private void SendInput()
 				AddOutputText("> " + this.inputTextBox.Text);
 
 			this.teletypeDevice.AddInputLine(this.inputTextBox.Text);
-			this.inputTextBox.Text = "";
+			this.inputTextBox.Text = string.Empty;
 			this.toolStripStatusLabel.Text = "Sent input to Mix";
 		}
 

src/MixEmul/Components/ToolStripCycleButton.cs

@@ -22,7 +22,7 @@ public ToolStripCycleButton(IContainer container) : this()
 			=> container.Add(this);
 
 		public ToolStripCycleButton()
-			: base(new Button { Text = "", FlatStyle = FlatStyle.Flat, Height = 21, Padding = new Padding(0), TextAlign = ContentAlignment.TopCenter })
+			: base(new Button { Text = string.Empty, FlatStyle = FlatStyle.Flat, Height = 21, Padding = new Padding(0), TextAlign = ContentAlignment.TopCenter })
 		{
 			InitializeComponent();
 			this.steps = new List<Step>();
@@ -31,7 +31,7 @@ public ToolStripCycleButton()
 			Control.SizeChanged += Control_SizeChanged;
 			Control.Click += Control_Click;
 			Control.Paint += ToolStripCycleButton_Paint;
-			Text = "";
+			Text = string.Empty;
 		}
 
 		protected void OnValueChanged(EventArgs e)