diff --git a/src/Highlighter.php b/src/Highlighter.php
index ebce86ca..b33d8dbf 100644
--- a/src/Highlighter.php
+++ b/src/Highlighter.php
@@ -10,6 +10,7 @@
 use Tempest\Highlight\Languages\Bash\BashLanguage;
 use Tempest\Highlight\Languages\BBCode\BBCodeLanguage;
 use Tempest\Highlight\Languages\Blade\BladeLanguage;
+use Tempest\Highlight\Languages\CSharp\CSharpLanguage;
 use Tempest\Highlight\Languages\C\CLanguage;
 use Tempest\Highlight\Languages\Cpp\CppLanguage;
 use Tempest\Highlight\Languages\Css\CssLanguage;
@@ -78,6 +79,7 @@ public function __construct(
             ->addLanguage(new BashLanguage())
             ->addLanguage(new BBCodeLanguage())
             ->addLanguage(new BladeLanguage())
+            ->addLanguage(new CSharpLanguage())
             ->addLanguage(new CLanguage())
             ->addLanguage(new CppLanguage())
             ->addLanguage(new CssLanguage())
diff --git a/src/Languages/CSharp/CSharpLanguage.php b/src/Languages/CSharp/CSharpLanguage.php
new file mode 100644
index 00000000..c0b0fecc
--- /dev/null
+++ b/src/Languages/CSharp/CSharpLanguage.php
@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp;
+
+use Override;
+use Tempest\Highlight\Languages\Base\BaseLanguage;
+use Tempest\Highlight\Languages\CLike\Patterns\CLikeCommentPattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpAttributePattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpCallablePattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpDeclarationPattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpDelegatePattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpKeywordPattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpLiteralPattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpNamespacePattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpNumberPattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpOperatorPattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpPreprocessorPattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpPropertyPattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpStringPattern;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpTypePattern;
+
+final class CSharpLanguage extends BaseLanguage
+{
+    public function getName(): string
+    {
+        return 'csharp';
+    }
+
+    #[Override]
+    public function getAliases(): array
+    {
+        return ['cs', 'c#'];
+    }
+
+    #[Override]
+    public function getPatterns(): array
+    {
+        return [
+            ...parent::getPatterns(),
+            new CLikeCommentPattern(),
+            new CSharpStringPattern(),
+            new CSharpPreprocessorPattern(),
+            new CSharpAttributePattern(),
+            new CSharpNamespacePattern(),
+            new CSharpNumberPattern(),
+            new CSharpLiteralPattern(),
+            new CSharpKeywordPattern(),
+            new CSharpDeclarationPattern(),
+            new CSharpDelegatePattern(),
+            new CSharpCallablePattern(),
+            new CSharpPropertyPattern(),
+            new CSharpTypePattern(),
+            new CSharpOperatorPattern(),
+        ];
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpAttributePattern.php b/src/Languages/CSharp/Patterns/CSharpAttributePattern.php
new file mode 100644
index 00000000..82bbdf1b
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpAttributePattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: '[Obsolete]', output: 'Obsolete')]
+#[PatternTest(input: '[assembly: Guid("x")]', output: 'Guid')]
+final readonly class CSharpAttributePattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '\[\h*(?:(?:assembly|module|field|event|method|param|property|return|type):\h*)?(?<match>[A-Za-z_]\w*(?:\.[A-Za-z_]\w*)*(?:Attribute)?)';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::ATTRIBUTE;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpCallablePattern.php b/src/Languages/CSharp/Patterns/CSharpCallablePattern.php
new file mode 100644
index 00000000..ddde4026
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpCallablePattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: 'Render()', output: 'Render')]
+#[PatternTest(input: 'Method<int>()', output: 'Method')]
+final readonly class CSharpCallablePattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '(?<![\w@])(?!(?:catch|checked|do|for|foreach|if|lock|sizeof|switch|typeof|unchecked|using|while)\b)(?<match>@?[A-Za-z_]\w*)(?=\h*(?:<[^<>]*>\h*)?\()';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::PROPERTY;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpDeclarationPattern.php b/src/Languages/CSharp/Patterns/CSharpDeclarationPattern.php
new file mode 100644
index 00000000..58e557de
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpDeclarationPattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: 'class User {}', output: 'User')]
+#[PatternTest(input: 'record Point(int X);', output: 'Point')]
+final readonly class CSharpDeclarationPattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '\b(?:class|interface|struct|record|enum)\h+(?<match>@?[A-Za-z_]\w*)';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::TYPE;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpDelegatePattern.php b/src/Languages/CSharp/Patterns/CSharpDelegatePattern.php
new file mode 100644
index 00000000..0ad0faf5
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpDelegatePattern.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: 'delegate int Callback(int value);', output: 'Callback')]
+final readonly class CSharpDelegatePattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '\bdelegate\h+(?:[A-Za-z_]\w*(?:\h*<[^<>]*>)?(?:\h*\[\h*])?\??)\h+(?<match>@?[A-Za-z_]\w*)(?=\h*(?:<[^<>]*>\h*)?\()';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::TYPE;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpKeywordPattern.php b/src/Languages/CSharp/Patterns/CSharpKeywordPattern.php
new file mode 100644
index 00000000..8593c50f
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpKeywordPattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: 'namespace Example;', output: 'namespace')]
+#[PatternTest(input: 'async Task Run()', output: 'async')]
+final readonly class CSharpKeywordPattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '\b(?<match>abstract|add|alias|and|as|ascending|async|await|base|break|by|case|catch|checked|class|const|continue|default|delegate|descending|do|else|enum|equals|event|explicit|extern|file|finally|fixed|for|foreach|from|get|global|goto|group|if|implicit|in|init|interface|internal|into|is|join|let|lock|managed|nameof|namespace|new|not|notnull|on|operator|or|orderby|out|override|params|partial|private|protected|public|readonly|record|ref|remove|required|return|scoped|sealed|select|set|sizeof|stackalloc|static|struct|switch|this|throw|try|typeof|unchecked|unmanaged|unsafe|using|value|virtual|volatile|when|where|while|with|yield)\b';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::KEYWORD;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpLiteralPattern.php b/src/Languages/CSharp/Patterns/CSharpLiteralPattern.php
new file mode 100644
index 00000000..52c24183
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpLiteralPattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: 'true', output: 'true')]
+#[PatternTest(input: 'null', output: 'null')]
+final readonly class CSharpLiteralPattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '\b(?<match>true|false|null)\b';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::LITERAL;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpNamespacePattern.php b/src/Languages/CSharp/Patterns/CSharpNamespacePattern.php
new file mode 100644
index 00000000..b79cf616
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpNamespacePattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: 'namespace Example.App;', output: 'Example.App')]
+#[PatternTest(input: 'using System.Text;', output: 'System.Text')]
+final readonly class CSharpNamespacePattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '\b(?:namespace|using)\h+(?:static\h+|global\h+)?(?:[A-Za-z_]\w*\h*=\h*)?(?<match>(?:global::)?[A-Za-z_]\w*(?:\.[A-Za-z_]\w*)*)';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::TYPE;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpNumberPattern.php b/src/Languages/CSharp/Patterns/CSharpNumberPattern.php
new file mode 100644
index 00000000..42c29335
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpNumberPattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: '1_000m', output: '1_000m')]
+#[PatternTest(input: '0xFF', output: '0xFF')]
+final readonly class CSharpNumberPattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '/(?<![\w.])(?<match>(?:0[xX][\dA-Fa-f](?:_?[\dA-Fa-f])*|0[bB][01](?:_?[01])*|(?:\d(?:_?\d)*(?:\.\d(?:_?\d)*)?|\.\d(?:_?\d)*)(?:[eE][+-]?\d(?:_?\d)*)?)(?:[uUlLfFdDmM]{1,2})?)(?![\w.])/';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::NUMBER;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpOperatorPattern.php b/src/Languages/CSharp/Patterns/CSharpOperatorPattern.php
new file mode 100644
index 00000000..012191af
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpOperatorPattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: 'x => x + 1', output: '=>')]
+#[PatternTest(input: 'user?.Name', output: '?.')]
+final readonly class CSharpOperatorPattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '/(?<match>=>|\?\?=|\?\?|\?\.|\?\[|\.\.|<<=?|>>=?|\+\+|--|&&|\|\||==|!=|<=|>=|[-+*\/%&|^~!<>=]=?|[?:;,.{}()\[\]])/';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::OPERATOR;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpPreprocessorPattern.php b/src/Languages/CSharp/Patterns/CSharpPreprocessorPattern.php
new file mode 100644
index 00000000..732ef68e
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpPreprocessorPattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: '#nullable enable', output: '#nullable')]
+#[PatternTest(input: '#region Setup', output: '#region')]
+final readonly class CSharpPreprocessorPattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '/(?m)^\h*(?<match>#\h*(?:define|undef|if|elif|else|endif|line|error|warning|region|endregion|pragma|nullable|r|load)\b)/';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::KEYWORD;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpPropertyPattern.php b/src/Languages/CSharp/Patterns/CSharpPropertyPattern.php
new file mode 100644
index 00000000..bc1e0b5b
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpPropertyPattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: 'user.Name', output: 'Name')]
+#[PatternTest(input: 'Name { get; }', output: 'Name')]
+final readonly class CSharpPropertyPattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '/(?:(?:\?\.|\.)\K|(?<![\w@])(?=@?[A-Za-z_]\w*\h*(?:\{|=>)))(?<match>@?[A-Za-z_]\w*)(?!\h*\()/';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::PROPERTY;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpStringPattern.php b/src/Languages/CSharp/Patterns/CSharpStringPattern.php
new file mode 100644
index 00000000..dd8c7eca
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpStringPattern.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: '$"Hello {name}"', output: '$"Hello {name}"')]
+#[PatternTest(input: '"""hello"""', output: '"""hello"""')]
+#[PatternTest(input: '\'x\'', output: '\'x\'')]
+final readonly class CSharpStringPattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '/(?<match>\$*+(?<delimiter>"{3,})(?:(?!\k<delimiter>)[\s\S])*+\k<delimiter>|(?:\$@|@\$|@)"(?:[^"]++|"")*+"|\$?"(?:\\\\.|[^"\\\\\r\n]++)*+"|\'(?:\\\\.|[^\'\\\\\r\n])\')/';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::VALUE;
+    }
+}
diff --git a/src/Languages/CSharp/Patterns/CSharpTypePattern.php b/src/Languages/CSharp/Patterns/CSharpTypePattern.php
new file mode 100644
index 00000000..c274a5fd
--- /dev/null
+++ b/src/Languages/CSharp/Patterns/CSharpTypePattern.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Languages\CSharp\Patterns;
+
+use Tempest\Highlight\IsPattern;
+use Tempest\Highlight\Pattern;
+use Tempest\Highlight\PatternTest;
+use Tempest\Highlight\Tokens\TokenTypeEnum;
+
+#[PatternTest(input: 'string', output: 'string')]
+#[PatternTest(input: 'User', output: 'User')]
+final readonly class CSharpTypePattern implements Pattern
+{
+    use IsPattern;
+
+    public function getPattern(): string
+    {
+        return '\b(?<match>bool|byte|sbyte|char|decimal|double|float|int|uint|nint|nuint|long|ulong|short|ushort|object|string|void|dynamic|var|(?<!\[)[A-Z][A-Za-z0-9_]*)\b';
+    }
+
+    public function getTokenType(): TokenTypeEnum
+    {
+        return TokenTypeEnum::TYPE;
+    }
+}
diff --git a/tests/Bench/Fixtures/csharp.txt b/tests/Bench/Fixtures/csharp.txt
new file mode 100644
index 00000000..18b8ffc4
--- /dev/null
+++ b/tests/Bench/Fixtures/csharp.txt
@@ -0,0 +1,39 @@
+#nullable enable
+
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Demo.Highlight;
+
+/// <summary>Formats immutable events for the audit stream.</summary>
+[AttributeUsage(AttributeTargets.Class)]
+public sealed class AuditedAttribute : Attribute {}
+
+public readonly record struct Event<T>(Guid Id, string Name, T Payload);
+
+public interface IRepository<T> where T : notnull
+{
+    IAsyncEnumerable<T> StreamAsync(CancellationToken cancellationToken = default);
+}
+
+[Audited]
+public sealed class EventFormatter
+{
+    private const decimal Rate = 12.5m;
+    private const string Root = @"C:\logs";
+
+    public required string Prefix { get; init; }
+
+    public async Task<string> FormatAsync<T>(Event<T>? item) where T : notnull
+    {
+        ArgumentNullException.ThrowIfNull(item);
+
+        var names = from value in new[] { item.Name }
+                    where !string.IsNullOrWhiteSpace(value)
+                    select value.Trim();
+
+        await Task.Yield();
+
+        return $"""{Prefix}: {string.Join(", ", names)} ({item.Payload})""";
+    }
+}
diff --git a/tests/Bench/HighlighterBench.php b/tests/Bench/HighlighterBench.php
index 675023e7..857ddfd0 100644
--- a/tests/Bench/HighlighterBench.php
+++ b/tests/Bench/HighlighterBench.php
@@ -21,6 +21,7 @@ final class HighlighterBench
         'bash' => 'bash.txt',
         'bbcode' => 'bbcode.txt',
         'blade' => 'blade.txt',
+        'csharp' => 'csharp.txt',
         'c' => 'c.txt',
         'cpp' => 'cpp.txt',
         'css' => 'css.txt',
diff --git a/tests/Languages/CSharp/CSharpLanguageTest.php b/tests/Languages/CSharp/CSharpLanguageTest.php
new file mode 100644
index 00000000..b47c0934
--- /dev/null
+++ b/tests/Languages/CSharp/CSharpLanguageTest.php
@@ -0,0 +1,134 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Highlight\Tests\Languages\CSharp;
+
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use Tempest\Highlight\Highlighter;
+use Tempest\Highlight\Languages\CLike\Patterns\CLikeCommentPattern;
+use Tempest\Highlight\Languages\CSharp\CSharpLanguage;
+use Tempest\Highlight\Languages\CSharp\Patterns\CSharpStringPattern;
+use Tempest\Highlight\Tests\Bench\HighlighterBench;
+
+final class CSharpLanguageTest extends TestCase
+{
+    #[Test]
+    public function it_registers_the_language_name_and_aliases(): void
+    {
+        $highlighter = new Highlighter();
+
+        foreach (['csharp', 'cs', 'c#'] as $name) {
+            $this->assertContains($name, $highlighter->getSupportedLanguageNames());
+
+            $highlighter->parse('', $name);
+
+            $this->assertInstanceOf(CSharpLanguage::class, $highlighter->getCurrentLanguage());
+        }
+    }
+
+    #[Test]
+    #[DataProvider('provide_it_highlights_representative_syntax_cases')]
+    public function it_highlights_representative_syntax(string $source, string $expected): void
+    {
+        $highlighted = (new Highlighter())->parse($source, 'csharp');
+
+        $this->assertStringContainsString($expected, $highlighted);
+    }
+
+    public static function provide_it_highlights_representative_syntax_cases(): iterable
+    {
+        yield 'preprocessor directive' => ['#nullable enable', '<span class="hl-keyword">#nullable</span>'];
+        yield 'namespace keyword' => ['namespace Demo.Tools;', '<span class="hl-keyword">namespace</span>'];
+        yield 'namespace name' => ['namespace Demo.Tools;', '<span class="hl-type">Demo<span class="hl-operator">.</span>Tools</span>'];
+        yield 'using directive' => ['using System.Text;', '<span class="hl-keyword">using</span>'];
+        yield 'attribute' => ['[Obsolete]', '<span class="hl-attribute">Obsolete</span>'];
+        yield 'line comment' => ['// note', '<span class="hl-comment">// note</span>'];
+        yield 'XML documentation' => ['/// <summary>Note</summary>', '<span class="hl-comment">/// &lt;summary&gt;Note&lt;/summary&gt;</span>'];
+        yield 'block comment' => ['/* note */', '<span class="hl-comment">/* note */</span>'];
+        yield 'regular string' => ['"hello\\n"', '<span class="hl-value">&quot;hello\\n&quot;</span>'];
+        yield 'verbatim string' => ['@"c:\\temp"', '<span class="hl-value">@&quot;c:\\temp&quot;</span>'];
+        yield 'interpolated string' => ['$"Hello {name}"', '<span class="hl-value">$&quot;Hello {name}&quot;</span>'];
+        yield 'raw string' => ['"""<tag>"""', '<span class="hl-value">&quot;&quot;&quot;&lt;tag&gt;&quot;&quot;&quot;</span>'];
+        yield 'character' => ["'x'", '<span class="hl-value">\'x\'</span>'];
+        yield 'number' => ['0xCAFE_F00DUL', '<span class="hl-number">0xCAFE_F00DUL</span>'];
+        yield 'keyword' => ['return', '<span class="hl-keyword">return</span>'];
+        yield 'modifier' => ['public', '<span class="hl-keyword">public</span>'];
+        yield 'built-in type' => ['string', '<span class="hl-type">string</span>'];
+        yield 'class' => ['class Widget {}', '<span class="hl-type">Widget</span>'];
+        yield 'interface' => ['interface IService {}', '<span class="hl-type">IService</span>'];
+        yield 'struct' => ['struct Point {}', '<span class="hl-type">Point</span>'];
+        yield 'record' => ['record User(int Id);', '<span class="hl-type">User</span>'];
+        yield 'enum' => ['enum Status {}', '<span class="hl-type">Status</span>'];
+        yield 'delegate' => ['delegate void Handler();', '<span class="hl-type">Handler</span>'];
+        yield 'generic type' => ['List<string> values;', '<span class="hl-type">List</span>'];
+        yield 'nullable type' => ['string? value;', '<span class="hl-type">string</span><span class="hl-operator">?</span>'];
+        yield 'literal' => ['return null;', '<span class="hl-literal">null</span>'];
+        yield 'method call' => ['Render();', '<span class="hl-property">Render</span>'];
+        yield 'property' => ['public string Name { get; init; }', '<span class="hl-property">Name</span>'];
+        yield 'lambda' => ['value => value + 1', '<span class="hl-operator">=&gt;</span>'];
+        yield 'query expression' => ['from item in items select item', '<span class="hl-keyword">from</span>'];
+        yield 'operator' => ['left ?? right', '<span class="hl-operator">??</span>'];
+        yield 'punctuation' => ['return value;', '<span class="hl-operator">;</span>'];
+    }
+
+    #[Test]
+    public function it_escapes_html_and_strips_reserved_markers(): void
+    {
+        $source = "class Markup {\r\n"
+            . "    string Value = \"<&copy;> ❷img src=x onerror=alert(1)❸ ❶❹❿\";\r"
+            . "    string Script = \"<script>alert('x')</script>\";\r\n"
+            . "}\r\n";
+
+        $highlighted = (new Highlighter())->parse($source, 'csharp');
+        $renderedSource = html_entity_decode(strip_tags($highlighted), ENT_QUOTES | ENT_HTML5);
+
+        $expectedSource = str_replace(["\r\n", "\r"], "\n", str_replace(['❶', '❷', '❸', '❹', '❿'], '', $source));
+
+        $this->assertSame($expectedSource, $renderedSource);
+        $this->assertStringNotContainsString('<script>', $highlighted);
+        $this->assertStringNotContainsString('<img', $highlighted);
+        $this->assertStringContainsString('&lt;script&gt;', $highlighted);
+        $this->assertStringContainsString('&amp;copy;', $highlighted);
+    }
+
+    #[Test]
+    public function it_has_non_empty_a_non_empty_benchmark_fixture(): void
+    {
+        $this->assertSame('csharp.txt', HighlighterBench::LANGUAGES['csharp'] ?? null);
+
+        foreach ([__DIR__ . '/../../Bench/Fixtures/csharp.txt'] as $fixture) {
+            $this->assertFileExists($fixture);
+            $this->assertNotSame('', trim((string) file_get_contents($fixture)));
+        }
+    }
+
+    #[Test]
+    public function it_avoids_backtracking_errors_for_unterminated_comments_and_strings(): void
+    {
+        $patterns = (new CSharpLanguage())->getPatterns();
+        $commentPattern = array_find(
+            $patterns,
+            static fn (object $pattern): bool => $pattern instanceof CLikeCommentPattern,
+        );
+        $stringPattern = array_find(
+            $patterns,
+            static fn (object $pattern): bool => $pattern instanceof CSharpStringPattern,
+        );
+
+        $this->assertInstanceOf(CLikeCommentPattern::class, $commentPattern);
+        $this->assertInstanceOf(CSharpStringPattern::class, $stringPattern);
+
+        foreach ([
+            [$commentPattern, '/*' . str_repeat('a', 1_000)],
+            [$stringPattern, '"""' . str_repeat('a', 1_000)],
+            [$stringPattern, '$"' . str_repeat('a', 1_000)],
+        ] as [$pattern, $source]) {
+            $pattern->match($source);
+
+            $this->assertSame(PREG_NO_ERROR, preg_last_error(), preg_last_error_msg());
+        }
+    }
+}