Ported as conceptual article from .NET dev blog: Regex enhancements with .NET 7 (dotnet#31587)

* Initial bits and raw port

* Added to TOC

* Fix syntax error

* Minor updates and tweaks

* Minor update

* Updates, removals, clean up

* Fix names and paths

* Updates and fixes

* More updates and clean up

* Getting close

* More fixes and updates, and adjusted headings

* Finishing touches

* A bit more clean up

* Testing footnote extensions

* Testing diagram extensions

* Testing definition list support with markdig exts

* Add another footnote and code updates

* Ready for review

* Apply suggestions from code review

Co-authored-by: Genevieve Warren <[email protected]>

* Address additional feedback

* A bit of MD cleanup

Co-authored-by: Genevieve Warren <[email protected]>

Author: IEvangelist

docfx.json

@@ -1,6 +1,15 @@
 {
     "build": {
-        "markdownEngineName": "markdig",
+      "markdownEngineName": "markdig",
+      "markdownEngineProperties": {
+        "markdigExtensions": [
+            "abbreviations",
+            "definitionlists",
+            "tasklists",
+            "footnotes",
+            "diagrams"
+          ]
+        },
         "content": [
             {
                 "files": ["api/**/*.md"]

docs/fundamentals/toc.yml

@@ -2253,6 +2253,9 @@ items:
     - name: Overview
       href: ../standard/base-types/regular-expressions.md
       displayName: regular expressions
+    - name: Source generation
+      href: ../standard/base-types/regular-expression-source-generators.md
+      displayName: regular expressions,advanced,design concepts,source generators,algorithmic reduction,regex
     - name: Language reference
       items:
       - name: Overview

docs/standard/base-types/media/regular-expression-source-generators/cached-instance-fallback.png

@@ -23,6 +23,7 @@ helpviewer_keywords:
   - "strings [.NET], regular expressions"
 ms.assetid: 521b3f6d-f869-42e1-93e5-158c54a6895d
 ---
+
 # .NET regular expressions
 
 Regular expressions provide a powerful, flexible, and efficient method for processing text. The extensive pattern-matching notation of regular expressions enables you to quickly parse large amounts of text to:

docs/standard/base-types/media/regular-expression-source-generators/cached-instance.png

@@ -0,0 +1,64 @@
+using System.Text;
+using System.Text.RegularExpressions;
+
+static partial class Program
+{
+    private static readonly Regex s_abcOrDefGeneratedRegex = AbcOrDefGeneratedRegex();
+
+    [GeneratedRegex(
+        pattern: "abc|def",
+        options: RegexOptions.IgnoreCase | RegexOptions.Compiled,
+        cultureName: "en-US")]
+    private static partial Regex AbcOrDefGeneratedRegex();
+
+    private static void EvaluateText(string text)
+    {
+        if (s_abcOrDefGeneratedRegex.IsMatch(text))
+        {
+            Console.WriteLine($"""
+                ✅ "{text}" matches "{s_abcOrDefGeneratedRegex}" pattern.
+                """);
+        }
+        else
+        {
+            Console.WriteLine($"""
+                ❌ "{text}" doesn't match "{s_abcOrDefGeneratedRegex}" pattern.
+                """);
+        }
+    }
+
+    private static void Main()
+    {
+        Console.OutputEncoding = Encoding.UTF8;
+
+        new List<string> { "Incubus", "Deftones", "Tool" }.ForEach(EvaluateText);
+
+        // Sample output:
+        //   ❌ "Incubus" doesn't match "abc|def" pattern.
+        //   ✅ "Deftones" matches "abc|def" pattern.
+        //   ❌ "Tool" doesn't match "abc|def" pattern.
+
+        var abcOrDefRegex = new Regex(pattern: "abc|def", options: RegexOptions.IgnoreCase);
+    }
+}
+
+static file partial class Program
+{
+    [GeneratedRegex(pattern: @"(a|bc)d")]
+    private static partial Regex ExampleRegex();
+
+    [GeneratedRegex(pattern: "[ab]*[bc]")]
+    private static partial Regex AnotherExampleRegex();
+
+    [GeneratedRegex(pattern: "Monday|Tuesday|Wednesday|Thursday|Friday|Saturday|Sunday")]
+    private static partial Regex DaysOfWeekRegex();
+
+    [GeneratedRegex(pattern: "")]
+    private static partial Regex BlankRegex();
+
+    [GeneratedRegex(pattern: @"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$")]
+    private static partial Regex EmailRegex();
+
+    [GeneratedRegex(pattern: "(\\w)\\1")]
+    private static partial Regex WordWithBacktrackingRegex();
+}