Fix a few IndexOf{Any} uses

src/libraries/Microsoft.Win32.Registry/src/Microsoft/Win32/RegistryKey.cs

@@ -728,16 +728,16 @@ private static void ValidateKeyName(string name)
                 throw new ArgumentNullException(nameof(name));
             }
 
-            int nextSlash = name.IndexOf("\\", StringComparison.OrdinalIgnoreCase);
+            int nextSlash = name.IndexOf('\\');
             int current = 0;
-            while (nextSlash != -1)
+            while (nextSlash >= 0)
             {
                 if ((nextSlash - current) > MaxKeyLength)
                 {
                     throw new ArgumentException(SR.Arg_RegKeyStrLenBug, nameof(name));
                 }
                 current = nextSlash + 1;
-                nextSlash = name.IndexOf("\\", current, StringComparison.OrdinalIgnoreCase);
+                nextSlash = name.IndexOf('\\', current);
             }
 
             if ((name.Length - current) > MaxKeyLength)

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/AuthenticationHelper.Digest.cs

@@ -422,31 +422,25 @@ private void Parse(string challenge)
 
     internal static class StringBuilderExtensions
     {
-        // Characters that require escaping in quoted string
-        private static readonly char[] SpecialCharacters = new[] { '"', '\\' };
-
         public static void AppendKeyValue(this StringBuilder sb, string key, string value, bool includeQuotes = true, bool includeComma = true)
         {
-            sb.Append(key);
-            sb.Append('=');
+            sb.Append(key).Append('=');
+
             if (includeQuotes)
             {
+                ReadOnlySpan<char> valueSpan = value;
                 sb.Append('"');
-                int lastSpecialIndex = 0;
-                int specialIndex;
                 while (true)
                 {
-                    specialIndex = value.IndexOfAny(SpecialCharacters, lastSpecialIndex);
-                    if (specialIndex >= 0)
+                    int i = valueSpan.IndexOfAny('"', '\\'); // Characters that require escaping in quoted string
+                    if (i >= 0)
                     {
-                        sb.Append(value, lastSpecialIndex, specialIndex - lastSpecialIndex);
-                        sb.Append('\\');
-                        sb.Append(value[specialIndex]);
-                        lastSpecialIndex = specialIndex + 1;
+                        sb.Append(valueSpan.Slice(0, i)).Append('\\').Append(valueSpan[i]);
+                        valueSpan = valueSpan.Slice(i + 1);
                     }
                     else
                     {
-                        sb.Append(value, lastSpecialIndex, value.Length - lastSpecialIndex);
+                        sb.Append(valueSpan);
                         break;
                     }
                 }
@@ -459,8 +453,7 @@ public static void AppendKeyValue(this StringBuilder sb, string key, string valu
 
             if (includeComma)
             {
-                sb.Append(',');
-                sb.Append(' ');
+                sb.Append(',').Append(' ');
             }
         }
     }

src/libraries/System.Net.Mail/src/System/Net/Mail/Attachment.cs

@@ -12,7 +12,6 @@ public abstract class AttachmentBase : IDisposable
     {
         internal bool disposed;
         private readonly MimePart _part = new MimePart();
-        private static readonly char[] s_contentCIDInvalidChars = new char[] { '<', '>' };
 
         internal AttachmentBase()
         {
@@ -248,7 +247,7 @@ public string ContentId
                 }
                 else
                 {
-                    if (value.IndexOfAny(s_contentCIDInvalidChars) != -1)
+                    if (value.AsSpan().IndexOfAny('<', '>') >= 0) // invalid chars
                     {
                         throw new ArgumentException(SR.MailHeaderInvalidCID, nameof(value));
                     }

src/libraries/System.Private.CoreLib/src/System/Globalization/CultureData.cs

@@ -2094,7 +2094,7 @@ private static string GetSeparator(string format, string timeParts)
         private static int IndexOfTimePart(string format, int startIndex, string timeParts)
         {
             Debug.Assert(startIndex >= 0, "startIndex cannot be negative");
-            Debug.Assert(timeParts.IndexOfAny(new char[] { '\'', '\\' }) < 0, "timeParts cannot include quote characters");
+            Debug.Assert(timeParts.AsSpan().IndexOfAny('\'', '\\') < 0, "timeParts cannot include quote characters");
             bool inQuote = false;
             for (int i = startIndex; i < format.Length; ++i)
             {

src/libraries/System.Private.CoreLib/src/System/Security/SecurityElement.cs

@@ -18,9 +18,6 @@ public sealed class SecurityElement
         private const int AttributesTypical = 4 * 2;  // 4 attributes, times 2 strings per attribute
         private const int ChildrenTypical = 1;
 
-        private static readonly char[] s_tagIllegalCharacters = new char[] { ' ', '<', '>' };
-        private static readonly char[] s_textIllegalCharacters = new char[] { '<', '>' };
-        private static readonly char[] s_valueIllegalCharacters = new char[] { '<', '>', '\"' };
         private static readonly char[] s_escapeChars = new char[] { '<', '>', '\"', '\'', '&' };
         private static readonly string[] s_escapeStringPairs = new string[]
         {
@@ -298,34 +295,17 @@ public SecurityElement Copy()
             return element;
         }
 
-        public static bool IsValidTag([NotNullWhen(true)] string? tag)
-        {
-            if (tag == null)
-                return false;
-
-            return tag.IndexOfAny(s_tagIllegalCharacters) < 0;
-        }
-
-        public static bool IsValidText([NotNullWhen(true)] string? text)
-        {
-            if (text == null)
-                return false;
+        public static bool IsValidTag([NotNullWhen(true)] string? tag) =>
+            tag != null && tag.AsSpan().IndexOfAny(' ', '<', '>') < 0;
 
-            return text.IndexOfAny(s_textIllegalCharacters) < 0;
-        }
-
-        public static bool IsValidAttributeName([NotNullWhen(true)] string? name)
-        {
-            return IsValidTag(name);
-        }
+        public static bool IsValidText([NotNullWhen(true)] string? text) =>
+            text != null && text.AsSpan().IndexOfAny('<', '>') < 0;
 
-        public static bool IsValidAttributeValue([NotNullWhen(true)] string? value)
-        {
-            if (value == null)
-                return false;
+        public static bool IsValidAttributeName([NotNullWhen(true)] string? name) =>
+            IsValidTag(name);
 
-            return value.IndexOfAny(s_valueIllegalCharacters) < 0;
-        }
+        public static bool IsValidAttributeValue([NotNullWhen(true)] string? value) =>
+            value != null && value.AsSpan().IndexOfAny('<', '>', '\"') < 0;
 
         private static string GetEscapeSequence(char c)
         {

src/libraries/System.Private.Xml/src/System/Xml/Xsl/Xslt/QilGenerator.cs

@@ -1055,16 +1055,14 @@ private QilNode CompileAvt(string source)
             return result;
         }
 
-        private static readonly char[] s_curlyBraces = { '{', '}' };
-
         [return: NotNullIfNotNull("avt")]
         private QilNode? CompileStringAvt(string? avt)
         {
             if (avt == null)
             {
                 return null;
             }
-            if (avt.IndexOfAny(s_curlyBraces) == -1)
+            if (avt.AsSpan().IndexOfAny('{', '}') < 0)
             {
                 return _f.String(avt);
             }
@@ -1074,7 +1072,7 @@ private QilNode CompileAvt(string source)
         private QilNode CompileTextAvt(string avt)
         {
             Debug.Assert(avt != null);
-            if (avt.IndexOfAny(s_curlyBraces) == -1)
+            if (avt.AsSpan().IndexOfAny('{', '}') < 0)
             {
                 return _f.TextCtor(_f.String(avt));
             }

src/libraries/System.Web.HttpUtility/src/System/Web/Util/UriUtil.cs

@@ -7,15 +7,13 @@ namespace System.Web.Util
 {
     internal static class UriUtil
     {
-        private static readonly char[] s_queryFragmentSeparators = { '?', '#' };
-
         // Just extracts the query string and fragment from the input path by splitting on the separator characters.
         // Doesn't perform any validation as to whether the input represents a valid URL.
         // Concatenating the pieces back together will form the original input string.
         private static void ExtractQueryAndFragment(string input, out string path, out string? queryAndFragment)
         {
-            int queryFragmentSeparatorPos = input.IndexOfAny(s_queryFragmentSeparators);
-            if (queryFragmentSeparatorPos != -1)
+            int queryFragmentSeparatorPos = input.AsSpan().IndexOfAny('?', '#'); // query fragment separators
+            if (queryFragmentSeparatorPos >= 0)
             {
                 path = input.Substring(0, queryFragmentSeparatorPos);
                 queryAndFragment = input.Substring(queryFragmentSeparatorPos);