Add missing regex description (#48299)

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Author: adegeo

docs/standard/base-types/character-classes-in-regular-expressions.md

@@ -0,0 +1,349 @@
+using System.Text.RegularExpressions;
+
+// Call all the example methods
+PositiveCharacterGroup();
+Console.WriteLine();
+
+CharacterRange();
+Console.WriteLine();
+
+NegativeCharacterGroup();
+Console.WriteLine();
+
+AnyCharacterSingleline();
+Console.WriteLine();
+
+AnyCharacterMultiline();
+Console.WriteLine();
+
+UnicodeCategory();
+Console.WriteLine();
+
+NegativeUnicodeCategory();
+Console.WriteLine();
+
+WordCharacter();
+Console.WriteLine();
+
+NonWordCharacter();
+Console.WriteLine();
+
+WhitespaceCharacter();
+Console.WriteLine();
+
+NonWhitespaceCharacter();
+Console.WriteLine();
+
+DigitCharacter();
+Console.WriteLine();
+
+NonDigitCharacter();
+Console.WriteLine();
+
+GetUnicodeCategory();
+Console.WriteLine();
+
+CharacterClassSubtraction();
+
+// <PositiveCharacterGroup>
+static void PositiveCharacterGroup()
+{
+    string pattern = @"gr[ae]y\s\S+?[\s\p{P}]";
+    string input = "The gray wolf jumped over the grey wall.";
+    MatchCollection matches = Regex.Matches(input, pattern);
+    foreach (Match match in matches)
+        Console.WriteLine($"'{match.Value}'");
+}
+// The example displays the following output:
+//       'gray wolf '
+//       'grey wall.'
+// </PositiveCharacterGroup>
+
+// <CharacterRange>
+static void CharacterRange()
+{
+    string pattern = @"\b[A-Z]\w*\b";
+    string input = "A city Albany Zulu maritime Marseilles";
+    foreach (Match match in Regex.Matches(input, pattern))
+        Console.WriteLine(match.Value);
+}
+// The example displays the following output:
+//       A
+//       Albany
+//       Zulu
+//       Marseilles
+// </CharacterRange>
+
+// <NegativeCharacterGroup>
+static void NegativeCharacterGroup()
+{
+    string pattern = @"\bth[^o]\w+\b";
+    string input = "thought thing though them through thus thorough this";
+    foreach (Match match in Regex.Matches(input, pattern))
+        Console.WriteLine(match.Value);
+}
+// The example displays the following output:
+//       thing
+//       them
+//       through
+//       thus
+//       this
+// </NegativeCharacterGroup>
+
+// <AnyCharacterSingleline>
+static void AnyCharacterSingleline()
+{
+    string pattern = @"\b.*[.?!;:](\s|\z)";
+    string input = "this. what: is? go, thing.";
+    foreach (Match match in Regex.Matches(input, pattern))
+        Console.WriteLine(match.Value);
+}
+// The example displays the following output:
+//       this. what: is? go, thing.
+// </AnyCharacterSingleline>
+
+// <AnyCharacterMultiline>
+static void AnyCharacterMultiline()
+{
+    string pattern = "^.+";
+    string input = "This is one line and" + Environment.NewLine + "this is the second.";
+    foreach (Match match in Regex.Matches(input, pattern))
+        Console.WriteLine(Regex.Escape(match.Value));
+
+    Console.WriteLine();
+    foreach (Match match in Regex.Matches(input, pattern, RegexOptions.Singleline))
+        Console.WriteLine(Regex.Escape(match.Value));
+}
+// The example displays the following output:
+//       This\ is\ one\ line\ and\r
+//
+//       This\ is\ one\ line\ and\r\nthis\ is\ the\ second\.
+// </AnyCharacterMultiline>
+
+// <UnicodeCategory>
+static void UnicodeCategory()
+{
+    string pattern = @"\b(\p{IsGreek}+(\s)?)+\p{Pd}\s(\p{IsBasicLatin}+(\s)?)+";
+    string input = "Ελληνική Γλώσσα - Greek Language";
+
+    Console.WriteLine(Regex.IsMatch(input, pattern));        // Displays True.
+}
+// </UnicodeCategory>
+
+// <NegativeUnicodeCategory>
+static void NegativeUnicodeCategory()
+{
+    string pattern = @"(\P{Sc})+";
+
+    string[] values = { "$164,091.78", "£1,073,142.68", "73¢", "€120" };
+    foreach (string value in values)
+        Console.WriteLine(Regex.Match(value, pattern).Value);
+}
+// The example displays the following output:
+//       164,091.78
+//       1,073,142.68
+//       73
+//       120
+// </NegativeUnicodeCategory>
+
+// <WordCharacter>
+static void WordCharacter()
+{
+    string pattern = @"(\w)\1";
+    string[] words = { "trellis", "seer", "latter", "summer",
+                       "hoarse", "lesser", "aardvark", "stunned" };
+    foreach (string word in words)
+    {
+        Match match = Regex.Match(word, pattern);
+        if (match.Success)
+            Console.WriteLine($"'{match.Value}' found in '{word}' at position {match.Index}.");
+        else
+            Console.WriteLine($"No double characters in '{word}'.");
+    }
+}
+// The example displays the following output:
+//       'll' found in 'trellis' at position 3.
+//       'ee' found in 'seer' at position 1.
+//       'tt' found in 'latter' at position 2.
+//       'mm' found in 'summer' at position 2.
+//       No double characters in 'hoarse'.
+//       'ss' found in 'lesser' at position 2.
+//       'aa' found in 'aardvark' at position 0.
+//       'nn' found in 'stunned' at position 3.
+// </WordCharacter>
+
+// <NonWordCharacter>
+static void NonWordCharacter()
+{
+    string pattern = @"\b(\w+)(\W){1,2}";
+    string input = "The old, grey mare slowly walked across the narrow, green pasture.";
+    foreach (Match match in Regex.Matches(input, pattern))
+    {
+        Console.WriteLine(match.Value);
+        Console.Write("   Non-word character(s):");
+        CaptureCollection captures = match.Groups[2].Captures;
+        for (int ctr = 0; ctr < captures.Count; ctr++)
+            Console.Write(@"'{0}' (\u{1}){2}", captures[ctr].Value,
+                          Convert.ToUInt16(captures[ctr].Value[0]).ToString("X4"),
+                          ctr < captures.Count - 1 ? ", " : "");
+        Console.WriteLine();
+    }
+}
+// The example displays the following output:
+//       The
+//          Non-word character(s):' ' (\u0020)
+//       old,
+//          Non-word character(s):',' (\u002C), ' ' (\u0020)
+//       grey
+//          Non-word character(s):' ' (\u0020)
+//       mare
+//          Non-word character(s):' ' (\u0020)
+//       slowly
+//          Non-word character(s):' ' (\u0020)
+//       walked
+//          Non-word character(s):' ' (\u0020)
+//       across
+//          Non-word character(s):' ' (\u0020)
+//       the
+//          Non-word character(s):' ' (\u0020)
+//       narrow,
+//          Non-word character(s):',' (\u002C), ' ' (\u0020)
+//       green
+//          Non-word character(s):' ' (\u0020)
+//       pasture.
+//          Non-word character(s):'.' (\u002E)
+// </NonWordCharacter>
+
+// <WhitespaceCharacter>
+static void WhitespaceCharacter()
+{
+    string pattern = @"\b\w+(e)?s(\s|$)";
+    string input = "matches stores stops leave leaves";
+    foreach (Match match in Regex.Matches(input, pattern))
+        Console.WriteLine(match.Value);
+}
+// The example displays the following output:
+//       matches
+//       stores
+//       stops
+//       leaves
+// </WhitespaceCharacter>
+
+// <NonWhitespaceCharacter>
+static void NonWhitespaceCharacter()
+{
+    string pattern = @"\b(\S+)\s?";
+    string input = "This is the first sentence of the first paragraph. " +
+                          "This is the second sentence.\n" +
+                          "This is the only sentence of the second paragraph.";
+    foreach (Match match in Regex.Matches(input, pattern))
+        Console.WriteLine(match.Groups[1]);
+}
+// The example displays the following output:
+//    This
+//    is
+//    the
+//    first
+//    sentence
+//    of
+//    the
+//    first
+//    paragraph.
+//    This
+//    is
+//    the
+//    second
+//    sentence.
+//    This
+//    is
+//    the
+//    only
+//    sentence
+//    of
+//    the
+//    second
+//    paragraph.
+// </NonWhitespaceCharacter>
+
+// <DigitCharacter>
+static void DigitCharacter()
+{
+    string pattern = @"^(\(?\d{3}\)?[\s-])?\d{3}-\d{4}$";
+    string[] inputs = { "111 111-1111", "222-2222", "222 333-444",
+                        "(212) 111-1111", "111-AB1-1111",
+                        "212-111-1111", "01 999-9999" };
+
+    foreach (string input in inputs)
+    {
+        if (Regex.IsMatch(input, pattern))
+            Console.WriteLine(input + ": matched");
+        else
+            Console.WriteLine(input + ": match failed");
+    }
+}
+// The example displays the following output:
+//       111 111-1111: matched
+//       222-2222: matched
+//       222 333-444: match failed
+//       (212) 111-1111: matched
+//       111-AB1-1111: match failed
+//       212-111-1111: matched
+//       01 999-9999: match failed
+// </DigitCharacter>
+
+// <NonDigitCharacter>
+static void NonDigitCharacter()
+{
+    string pattern = @"^\D\d{1,5}\D*$";
+    string[] inputs = { "A1039C", "AA0001", "C18A", "Y938518" };
+
+    foreach (string input in inputs)
+    {
+        if (Regex.IsMatch(input, pattern))
+            Console.WriteLine(input + ": matched");
+        else
+            Console.WriteLine(input + ": match failed");
+    }
+}
+// The example displays the following output:
+//       A1039C: matched
+//       AA0001: match failed
+//       C18A: matched
+//       Y938518: match failed
+// </NonDigitCharacter>
+
+// <GetUnicodeCategory>
+static void GetUnicodeCategory()
+{
+    char[] chars = { 'a', 'X', '8', ',', ' ', '\u0009', '!' };
+
+    foreach (char ch in chars)
+        Console.WriteLine($"'{Regex.Escape(ch.ToString())}': {Char.GetUnicodeCategory(ch)}");
+}
+// The example displays the following output:
+//       'a': LowercaseLetter
+//       'X': UppercaseLetter
+//       '8': DecimalDigitNumber
+//       ',': OtherPunctuation
+//       '\ ': SpaceSeparator
+//       '\t': Control
+//       '!': OtherPunctuation
+// </GetUnicodeCategory>
+
+// <CharacterClassSubtraction>
+static void CharacterClassSubtraction()
+{
+    string[] inputs = { "123", "13579753", "3557798", "335599901" };
+    string pattern = @"^[0-9-[2468]]+$";
+
+    foreach (string input in inputs)
+    {
+        Match match = Regex.Match(input, pattern);
+        if (match.Success)
+            Console.WriteLine(match.Value);
+    }
+}
+// The example displays the following output:
+//       13579753
+//       335599901
+// </CharacterClassSubtraction>

docs/standard/base-types/snippets/character-classes-in-regular-expressions/csharp/Program.cs

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>