Clean up improper usage of linguistic string functions (dotnet#31968)

- Optimize ToUpperInvariant/ToLowerInvariant
- Also optimize static field TextInfo.Invariant
- Rewrite ToUpper/Lower(Invariant) call sites to use optimized method
- Fix some uses of culture-aware ToUpper / ToLower to use invariant culture
- Replace Trim().Length with IsNullOrWhiteSpace where appropriate
- Use ordinal StartsWith / EndsWith where appropriate
- Avoid calling CultureInfo.InvariantCulture where possible

src/libraries/Common/src/Interop/Linux/cgroups/Interop.cgroups.cs

@@ -173,7 +173,7 @@ internal static bool TryFindHierarchyMount(string mountInfoFilePath, string subs
                             // the end of the optional values.
 
                             const string Separator = " - ";
-                            int endOfOptionalFields = line.IndexOf(Separator);
+                            int endOfOptionalFields = line.IndexOf(Separator, StringComparison.Ordinal);
                             if (endOfOptionalFields == -1)
                             {
                                 // Malformed line.

src/libraries/Common/src/System/Data/Common/DbConnectionOptions.Common.cs

@@ -153,7 +153,7 @@ private static string GetKeyName(StringBuilder buffer)
             {
                 count--; // trailing whitespace
             }
-            return buffer.ToString(0, count).ToLower(CultureInfo.InvariantCulture);
+            return buffer.ToString(0, count).ToLowerInvariant();
         }
 
         private static string GetKeyValue(StringBuilder buffer, bool trimWhitespace)
@@ -445,7 +445,7 @@ private static Dictionary<string, string> SplitConnectionString(string connectio
                 CaptureCollection keyvalues = match.Groups[ValueIndex].Captures;
                 foreach (Capture keypair in match.Groups[KeyIndex].Captures)
                 {
-                    string keyname = (firstKey ? keypair.Value : keypair.Value.Replace("==", "=")).ToLower(CultureInfo.InvariantCulture);
+                    string keyname = (firstKey ? keypair.Value : keypair.Value.Replace("==", "=")).ToLowerInvariant();
                     string keyvalue = keyvalues[indexValue++].Value;
                     if (0 < keyvalue.Length)
                     {

src/libraries/Common/src/System/Drawing/ColorTranslator.cs

@@ -260,7 +260,7 @@ public static Color FromHtml(string htmlColor)
                     InitializeHtmlSysColorTable();
                 }
 
-                s_htmlSysColorTable!.TryGetValue(htmlColor.ToLower(CultureInfo.InvariantCulture), out c);
+                s_htmlSysColorTable!.TryGetValue(htmlColor.ToLowerInvariant(), out c);
             }
 
             // resort to type converter which will handle named colors

src/libraries/Common/src/System/Net/NetworkInformation/UnixCommandLinePing.cs

@@ -154,7 +154,7 @@ public static long ParseRoundTripTime(string pingOutput)
         {
             int timeIndex = pingOutput.IndexOf("time=", StringComparison.Ordinal);
             int afterTime = timeIndex + "time=".Length;
-            int msIndex = pingOutput.IndexOf("ms", afterTime);
+            int msIndex = pingOutput.IndexOf("ms", afterTime, StringComparison.Ordinal);
             int numLength = msIndex - afterTime - 1;
             string timeSubstring = pingOutput.Substring(afterTime, numLength);
             double parsedRtt = double.Parse(timeSubstring, CultureInfo.InvariantCulture);

src/libraries/Microsoft.VisualBasic.Core/src/Microsoft/VisualBasic/CompilerServices/LikeOperator.vb

@@ -146,7 +146,7 @@ Namespace Microsoft.VisualBasic.CompilerServices
             WidthChanged = False
 
             If Length = 0 Then Return
-            Input = Input.ToLower(System.Globalization.CultureInfo.InvariantCulture)
+            Input = Input.ToLowerInvariant()
 
             Dim ExtraChars As Integer
 

src/libraries/Microsoft.VisualBasic.Core/src/Microsoft/VisualBasic/FileSystem.vb

@@ -75,7 +75,7 @@ Namespace Microsoft.VisualBasic
         End Sub
 
         Public Sub ChDrive(ByVal Drive As Char)
-            Drive = System.Char.ToUpper(Drive, CultureInfo.InvariantCulture)
+            Drive = System.Char.ToUpperInvariant(Drive)
 
             If (Drive < chLetterA) OrElse (Drive > chLetterZ) Then
                 Throw New ArgumentException(SR.Format(SR.Argument_InvalidValue1, "Drive"))
@@ -110,7 +110,7 @@ Namespace Microsoft.VisualBasic
             Debug.Assert(Not System.Reflection.Assembly.GetCallingAssembly() Is Utils.VBRuntimeAssembly,
                 "Methods in Microsoft.VisualBasic should not call FileSystem public method.")
 
-            Drive = System.Char.ToUpper(Drive, CultureInfo.InvariantCulture)
+            Drive = System.Char.ToUpperInvariant(Drive)
             If (Drive < chLetterA OrElse Drive > chLetterZ) Then
                 Throw VbMakeException(New ArgumentException(SR.Format(SR.Argument_InvalidValue1, "Drive")), vbErrors.DevUnavailable)
             End If

src/libraries/Microsoft.XmlSerializer.Generator/src/Sgen.cs

@@ -309,7 +309,7 @@ private void GenerateFile(List<string> typeNames, string assemblyName, bool prox
                     //However when a path ending with backslash, if followed by double quote, it becomes an escapte sequence
                     //e.g. "obj\Debug\netcoreapp2.0\", it will be converted as obj\Debug\netcoreapp2.0", which is not valid and not exist
                     //We need remove the ending quote for this situation
-                    if (!outputDirectory.EndsWith("\"") || !Directory.Exists(outputDirectory = outputDirectory.Remove(outputDirectory.Length - 1)))
+                    if (!outputDirectory.EndsWith("\"", StringComparison.Ordinal) || !Directory.Exists(outputDirectory = outputDirectory.Remove(outputDirectory.Length - 1)))
                     {
                         throw new ArgumentException(SR.Format(SR.ErrDirectoryNotExists, outputDirectory));
                     }

src/libraries/System.CodeDom/src/Microsoft/CSharp/CSharpCodeGenerator.cs

@@ -2703,7 +2703,7 @@ private string GetBaseTypeOutput(CodeTypeReference typeRef, bool preferBuiltInTy
                     return "void";
                 }
 
-                string lowerCaseString = s.ToLower(CultureInfo.InvariantCulture).Trim();
+                string lowerCaseString = s.ToLowerInvariant().Trim();
 
                 switch (lowerCaseString)
                 {

src/libraries/System.CodeDom/src/System/Collections/Specialized/FixedStringLookup.cs

@@ -44,7 +44,7 @@ private static bool Contains(string[] array, string value, bool ignoreCase)
             {
                 if (ignoreCase)
                 {
-                    searchChar = char.ToLower(value[pos], CultureInfo.InvariantCulture);
+                    searchChar = char.ToLowerInvariant(value[pos]);
                 }
                 else
                 {

src/libraries/System.ComponentModel.Annotations/src/System/ComponentModel/DataAnnotations/RequiredAttribute.cs

@@ -45,7 +45,7 @@ public override bool IsValid(object value)
             }
 
             // only check string length if empty strings are not allowed
-            return AllowEmptyStrings || !(value is string stringValue) || stringValue.Trim().Length != 0;
+            return AllowEmptyStrings || !(value is string stringValue) || !string.IsNullOrWhiteSpace(stringValue);
         }
     }
 }

src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/Design/DesigntimeLicenseContext.cs

@@ -99,7 +99,7 @@ public override string GetSavedLicenseKey(Type type, Assembly resourceAssembly)
 
                         if (s != null)
                         {
-                            DesigntimeLicenseContextSerializer.Deserialize(s, fileName.ToUpper(CultureInfo.InvariantCulture), this);
+                            DesigntimeLicenseContextSerializer.Deserialize(s, fileName.ToUpperInvariant(), this);
                             break;
                         }
                     }
@@ -140,7 +140,7 @@ public override string GetSavedLicenseKey(Type type, Assembly resourceAssembly)
                     }
                     if (s != null)
                     {
-                        DesigntimeLicenseContextSerializer.Deserialize(s, fileName.ToUpper(CultureInfo.InvariantCulture), this);
+                        DesigntimeLicenseContextSerializer.Deserialize(s, fileName.ToUpperInvariant(), this);
                     }
                 }
             }

src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/SyntaxCheck.cs

@@ -36,12 +36,12 @@ public static bool CheckPath(string value)
             if (value == null)
                 return false;
 
-            value = value.Trim();
+            value = value.TrimStart();
             if (value.Equals(string.Empty))
                 return false;
 
             // Path names should start with "\\"
-            return value.StartsWith("\\\\");
+            return value.StartsWith("\\\\", StringComparison.Ordinal);
         }
 
         /// <summary>

src/libraries/System.Composition.Hosting/src/System/Composition/Hosting/Util/Formatters.cs

@@ -46,7 +46,7 @@ private static string FormatClosedGeneric(Type closedGenericType)
                 throw new Exception(SR.Diagnostic_InternalExceptionMessage);
             }
 
-            var name = closedGenericType.Name.Substring(0, closedGenericType.Name.IndexOf("`"));
+            var name = closedGenericType.Name.Substring(0, closedGenericType.Name.IndexOf('`'));
             var args = closedGenericType.GenericTypeArguments.Select(t => Format(t));
             return string.Format("{0}<{1}>", name, string.Join(", ", args));
         }

src/libraries/System.Composition.Runtime/src/System/Composition/Runtime/Util/Formatters.cs

@@ -35,7 +35,7 @@ private static string FormatClosedGeneric(Type closedGenericType)
         {
             Debug.Assert(closedGenericType != null);
             Debug.Assert(closedGenericType.IsConstructedGenericType);
-            var name = closedGenericType.Name.Substring(0, closedGenericType.Name.IndexOf("`"));
+            var name = closedGenericType.Name.Substring(0, closedGenericType.Name.IndexOf('`'));
             IEnumerable<string> args = closedGenericType.GenericTypeArguments.Select(t => Format(t));
             return string.Format("{0}<{1}>", name, string.Join(SR.Formatter_ListSeparatorWithSpace, args));
         }

src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/ClientConfigPaths.cs

@@ -97,7 +97,7 @@ private ClientConfigPaths(string exePath, bool includeUserConfig)
             if (string.IsNullOrEmpty(namePrefix))
                 namePrefix = Validate(ProductName, limitSize: true);
             string applicationUriLower = !string.IsNullOrEmpty(ApplicationUri)
-                ? ApplicationUri.ToLower(CultureInfo.InvariantCulture)
+                ? ApplicationUri.ToLowerInvariant()
                 : null;
             string hashSuffix = GetTypeAndHashSuffix(applicationUriLower);
             string part2 = !string.IsNullOrEmpty(namePrefix) && !string.IsNullOrEmpty(hashSuffix)
@@ -272,7 +272,7 @@ private void SetNamesAndVersion(string applicationFilename, Assembly exeAssembly
                     // Try the remainder of the namespace
                     if (ns != null)
                     {
-                        int lastDot = ns.LastIndexOf(".", StringComparison.Ordinal);
+                        int lastDot = ns.LastIndexOf('.');
                         if ((lastDot != -1) && (lastDot < ns.Length - 1)) ProductName = ns.Substring(lastDot + 1);
                         else ProductName = ns;
 
@@ -291,7 +291,7 @@ private void SetNamesAndVersion(string applicationFilename, Assembly exeAssembly
                     // Try the first part of the namespace
                     if (ns != null)
                     {
-                        int firstDot = ns.IndexOf(".", StringComparison.Ordinal);
+                        int firstDot = ns.IndexOf('.');
                         _companyName = firstDot != -1 ? ns.Substring(0, firstDot) : ns;
 
                         _companyName = _companyName.Trim();

src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/ConfigurationElement.cs

@@ -1138,7 +1138,7 @@ protected internal virtual bool SerializeElement(XmlWriter writer, bool serializ
                     ((_itemLockedFlag & ConfigurationValueFlags.XmlParentInherited) == 0))
                 {
                     dataToWrite = true;
-                    writer?.WriteAttributeString(LockItemKey, true.ToString().ToLower(CultureInfo.InvariantCulture));
+                    writer?.WriteAttributeString(LockItemKey, true.ToString().ToLowerInvariant());
                 }
             }
 

src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/IdnElement.cs

@@ -50,11 +50,9 @@ public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceT
 
             public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
             {
-                string s = value as string;
-                if (s != null)
+                if (value is string s)
                 {
-                    s = s.ToLower(CultureInfo.InvariantCulture);
-                    switch (s)
+                    switch (s.ToLowerInvariant())
                     {
                         case "all":
                             return UriIdnScope.All;

src/libraries/System.Data.Common/src/System/Data/Common/AdapterUtil.Common.cs

@@ -788,7 +788,7 @@ internal static void BuildSchemaTableInfoTableNames(string[] columnNameArray)
                 string columnName = columnNameArray[i];
                 if ((null != columnName) && (0 < columnName.Length))
                 {
-                    columnName = columnName.ToLower(CultureInfo.InvariantCulture);
+                    columnName = columnName.ToLowerInvariant();
                     int index;
                     if (hash.TryGetValue(columnName, out index))
                     {
@@ -814,7 +814,7 @@ internal static void BuildSchemaTableInfoTableNames(string[] columnNameArray)
                 }
                 else
                 {
-                    columnName = columnName.ToLower(CultureInfo.InvariantCulture);
+                    columnName = columnName.ToLowerInvariant();
                     if (i != hash[columnName])
                     {
                         GenerateUniqueName(hash, ref columnNameArray[i], i, 1);
@@ -828,7 +828,7 @@ private static int GenerateUniqueName(Dictionary<string, int> hash, ref string c
             for (; ; ++uniqueIndex)
             {
                 string uniqueName = columnName + uniqueIndex.ToString(CultureInfo.InvariantCulture);
-                string lowerName = uniqueName.ToLower(CultureInfo.InvariantCulture);
+                string lowerName = uniqueName.ToLowerInvariant();
                 if (hash.TryAdd(lowerName, index))
                 {
                     columnName = uniqueName;

src/libraries/System.Data.Common/src/System/Data/Common/DbConnectionOptions.cs

@@ -167,7 +167,7 @@ internal string ExpandKeyword(string keyword, string replacementValue)
         [Conditional("DEBUG")]
         static partial void DebugTraceKeyValuePair(string keyname, string keyvalue, Dictionary<string, string> synonyms)
         {
-            Debug.Assert(keyname == keyname.ToLower(CultureInfo.InvariantCulture), "missing ToLower");
+            Debug.Assert(keyname == keyname.ToLowerInvariant(), "missing ToLower");
 
             string realkeyname = ((null != synonyms) ? (string)synonyms[keyname] : keyname);
             if ((KEY.Password != realkeyname) && (SYNONYM.Pwd != realkeyname))

src/libraries/System.Data.Common/src/System/Data/DataTable.cs

@@ -3711,9 +3711,9 @@ internal IndexField[] ParseSortString(string sortString)
                     }
 
                     // handle brackets.
-                    if (current.StartsWith("[", StringComparison.Ordinal))
+                    if (current.StartsWith('['))
                     {
-                        if (current.EndsWith("]", StringComparison.Ordinal))
+                        if (current.EndsWith(']'))
                         {
                             current = current.Substring(1, current.Length - 2);
                         }

src/libraries/System.Data.Common/src/System/Data/XMLSchema.cs

@@ -1161,7 +1161,7 @@ internal DataColumn FindField(DataTable table, string field)
             bool attribute = false;
             string colName = field;
 
-            if (field.StartsWith("@", StringComparison.Ordinal))
+            if (field.StartsWith('@'))
             {
                 attribute = true;
                 colName = field.Substring(1);

src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcConnection.cs

@@ -939,7 +939,7 @@ internal void Open_ChangeDatabase(string value)
             CheckState(ADP.ChangeDatabase);
 
             // Database name must not be null, empty or whitspace
-            if ((null == value) || (0 == value.Trim().Length))
+            if (string.IsNullOrWhiteSpace(value))
             { // MDAC 62679
                 throw ADP.EmptyDatabaseName();
             }

src/libraries/System.Data.OleDb/src/DbConnectionOptions.cs

@@ -484,7 +484,7 @@ internal string ExpandDataDirectories(ref string filename, ref int position)
         [System.Diagnostics.Conditional("DEBUG")]
         private static void DebugTraceKeyValuePair(string keyname, string keyvalue, Hashtable synonyms)
         {
-            Debug.Assert(keyname == keyname.ToLower(CultureInfo.InvariantCulture), "missing ToLower");
+            Debug.Assert(keyname == keyname.ToLowerInvariant(), "missing ToLower");
 
             string realkeyname = ((null != synonyms) ? (string)synonyms[keyname] : keyname);
             if ((KEY.Password != realkeyname) && (SYNONYM.Pwd != realkeyname))
@@ -505,7 +505,7 @@ private static string GetKeyName(StringBuilder buffer)
             {
                 count--; // trailing whitespace
             }
-            return buffer.ToString(0, count).ToLower(CultureInfo.InvariantCulture);
+            return buffer.ToString(0, count).ToLowerInvariant();
         }
 
         private static string GetKeyValue(StringBuilder buffer, bool trimWhitespace)
@@ -795,7 +795,7 @@ private static Hashtable SplitConnectionString(string connectionString, Hashtabl
                 CaptureCollection keyvalues = match.Groups[ValueIndex].Captures;
                 foreach (Capture keypair in match.Groups[KeyIndex].Captures)
                 {
-                    string keyname = (firstKey ? keypair.Value : keypair.Value.Replace("==", "=")).ToLower(CultureInfo.InvariantCulture);
+                    string keyname = (firstKey ? keypair.Value : keypair.Value.Replace("==", "=")).ToLowerInvariant();
                     string keyvalue = keyvalues[indexValue++].Value;
                     if (0 < keyvalue.Length)
                     {

src/libraries/System.Data.OleDb/src/OleDbCommandBuilder.cs

@@ -275,7 +275,7 @@ private static OleDbParameter[] DeriveParametersFromStoredProcedure(OleDbConnect
                                 value = dataRow[backendtype, DataRowVersion.Default];
                                 if (value is string)
                                 {
-                                    string backendtypename = ((string)value).ToLower(CultureInfo.InvariantCulture);
+                                    string backendtypename = ((string)value).ToLowerInvariant();
                                     switch (backendtypename)
                                     {
                                         case "binary":

src/libraries/System.Data.OleDb/src/OleDbConnection.cs

@@ -319,7 +319,7 @@ internal int QuotedIdentifierCase()
         public override void ChangeDatabase(string value)
         {
             CheckStateOpen(ADP.ChangeDatabase);
-            if ((null == value) || (0 == value.Trim().Length))
+            if (string.IsNullOrWhiteSpace(value))
             {
                 throw ADP.EmptyDatabaseName();
             }

src/libraries/System.Data.OleDb/src/OleDbConnectionString.cs

@@ -448,7 +448,7 @@ private static void ValidateProvider(string progid)
             {
                 throw ODB.InvalidProviderSpecified();
             }
-            progid = progid.ToLower(CultureInfo.InvariantCulture);
+            progid = progid.ToLowerInvariant();
             if (IsMSDASQL(progid))
             {
                 // fail msdasql even if not on the machine.

src/libraries/System.Data.OleDb/src/OleDbConnectionStringBuilder.cs

@@ -566,7 +566,7 @@ public override StandardValuesCollection GetStandardValues(ITypeDescriptorContex
                         if (DBSOURCETYPE_DATASOURCE_TDP == sourceType || DBSOURCETYPE_DATASOURCE_MDP == sourceType)
                         {
                             string progid = (string)row[column2];
-                            if (!OleDbConnectionString.IsMSDASQL(progid.ToLower(CultureInfo.InvariantCulture)))
+                            if (!OleDbConnectionString.IsMSDASQL(progid.ToLowerInvariant()))
                             {
                                 if (0 > providerNames.IndexOf(progid))
                                 {

src/libraries/System.Data.OleDb/src/OleDbDataReader.cs

@@ -1927,7 +1927,7 @@ private int IndexOf(Hashtable hash, string name)
             }
 
             // via case insensitive search, first match with lowest ordinal matches
-            string tmp = name.ToLower(CultureInfo.InvariantCulture);
+            string tmp = name.ToLowerInvariant();
             index = hash[tmp]; // match via lowercase
             return ((null != index) ? (int)index : -1);
         }
@@ -2027,7 +2027,7 @@ private void AppendSchemaInfo()
                 string basecolumname = _metadata[i].baseColumnName;
                 if (!ADP.IsEmpty(basecolumname))
                 {
-                    basecolumname = basecolumname.ToLower(CultureInfo.InvariantCulture);
+                    basecolumname = basecolumname.ToLowerInvariant();
                     if (!baseColumnNames.Contains(basecolumname))
                     {
                         baseColumnNames[basecolumname] = i;

src/libraries/System.Data.OleDb/src/PropertyInfoSet.cs

@@ -89,7 +89,7 @@ internal Dictionary<string, OleDbPropertyInfo> GetValues()
                             propertyInfo._vtype = propinfo.vtType;
                             propertyInfo._supportedValues = propinfo.vValue;
                             propertyInfo._description = propinfo.pwszDescription;
-                            propertyInfo._lowercase = propinfo.pwszDescription.ToLower(CultureInfo.InvariantCulture);
+                            propertyInfo._lowercase = propinfo.pwszDescription.ToLowerInvariant();
                             propertyInfo._type = PropertyInfoSet.FromVtType(propinfo.vtType);
 
                             propertyLookup[propertyInfo._lowercase] = propertyInfo;