Syntax highlighter for C#

gistfile1.cs

/// <summary>
/// A basic implementation of a pretty-printer or syntax highlighter for C# soure code.
/// </summary>
public class SourceColorer
{
	private string _commentCssClass;
	private string _keywordCssClass;
	private string _quotesCssClass;
	private string _typeCssClass;
	private bool _addStyleDefinition;
	private HashSet<string> _keywords;
	private bool _addPreTags;

	/// <summary>
	/// Gets the list of reserved words/keywords.
	/// </summary>
	public HashSet<string> Keywords
	{
		get { return _keywords; }
	}

	/// <summary>
	/// Gets or sets the CSS class used for comments. The default is 'comment'.
	/// </summary>
	public string CommentCssClass
	{
		get { return _commentCssClass; }
		set { _commentCssClass = value; }
	}

	/// <summary>
	/// Gets or sets the CSS class used for keywords. The default is 'keyword'.
	/// </summary>
	public string KeywordCssClass
	{
		get { return _keywordCssClass; }
		set { _keywordCssClass = value; }
	}

	/// <summary>
	/// Gets or sets the CSS class used for string quotes. The default is 'quotes'.
	/// </summary>
	public string QuotesCssClass
	{
		get { return _quotesCssClass; }
		set { _quotesCssClass = value; }
	}

	/// <summary>
	/// Gets or sets the CSS class used for types. The default is 'type'.
	/// </summary>
	public string TypeCssClass
	{
		get { return _typeCssClass; }
		set { _typeCssClass = value; }
	}

	/// <summary>
	/// Whether to add the CSS style definition to the top of the highlighted code.
	/// </summary>
	public bool AddStyleDefinition
	{
		get { return _addStyleDefinition; }
		set { _addStyleDefinition = value; }
	}

	/// <summary>
	/// Whether to insert opening and closing pre tags around the highlighted code.
	/// </summary>
	public bool AddPreTags
	{
		get { return _addPreTags; }
		set { _addPreTags = value; }
	}

	/// <summary>
	/// Initializes a new instance of the <see cref="SourceColorer"/> class.
	/// </summary>
	public SourceColorer()
	{
		_addStyleDefinition = true;
		_commentCssClass = "comment";
		_keywordCssClass = "keyword";
		_quotesCssClass = "quotes";
		_typeCssClass = "type";
		_keywords = new HashSet<string>()
		{
			"static", "using", "true", "false","new",
			"namespace", "void", "private", "public",
			"bool", "string", "return", "class","internal",
			"const", "readonly", "int", "double","lock",
			"float", "if", "else", "foreach", "for","var",
			"get","set","byte\\[\\]","char\\[\\]","int\\[\\]","string\\[\\]" // dumb array matching. Escaped as [] is regex syntax
		};
	}

	/// <summary>
	/// Highlights the specified source code and returns it as stylised HTML.
	/// </summary>
	/// <param name="source">The source code.</param>
	/// <returns></returns>
	public string Highlight(string source)
	{
		StringBuilder builder = new StringBuilder();
		if (AddStyleDefinition)
		{
			builder.Append("<style>");
			builder.AppendFormat(".{0}  {{ color: #0000FF  }} ", KeywordCssClass);
			builder.AppendFormat(".{0}  {{ color: #2B91AF  }} ", TypeCssClass);
			builder.AppendFormat(".{0}  {{ color: green    }} ", CommentCssClass);
			builder.AppendFormat(".{0}  {{ color: maroon   }} ", QuotesCssClass);
			builder.Append("</style>");
		}
		
		if (AddPreTags)
			builder.Append("<pre>");
			
		builder.Append(HighlightSource(source));
		
		if (AddPreTags)
			builder.Append("</pre>");
			
		return builder.ToString();
	}

	/// <summary>
	/// Occurs when the source code is highlighted, after any style (CSS) definitions are added.
	/// </summary>
	/// <param name="content">The source code content.</param>
	/// <returns>The highlighted source code.</returns>
	protected virtual string HighlightSource(string content)
	{
		if (string.IsNullOrEmpty(CommentCssClass))
			throw new InvalidOperationException("The CommentCssClass should not be null or empty");
		if (string.IsNullOrEmpty(KeywordCssClass))
			throw new InvalidOperationException("The KeywordCssClass should not be null or empty");
		if (string.IsNullOrEmpty(QuotesCssClass))
			throw new InvalidOperationException("The CommentCssClass should not be null or empty");
		if (string.IsNullOrEmpty(TypeCssClass))
			throw new InvalidOperationException("The TypeCssClass should not be null or empty");

		// Some fairly secure token placeholders
		const string COMMENTS_TOKEN = "`````";
		const string MULTILINECOMMENTS_TOKEN = "~~~~~";
		const string QUOTES_TOKEN = "¬¬¬¬¬";

		// Remove /* */ quotes, taken from ostermiller.org
		Regex regex = new Regex(@"/\*([^*]|[\r\n]|(\*+([^*/]|[\r\n])))*\*+/", RegexOptions.Singleline);
		List<string> multiLineComments = new List<string>();
		if (regex.IsMatch(content))
		{
			foreach (Match item in regex.Matches(content))
			{
				if (!multiLineComments.Contains(item.Value))
					multiLineComments.Add(item.Value);
			}
		}
		
		for (int i = 0; i < multiLineComments.Count; i++)
		{
			content = content.ReplaceToken(multiLineComments[i], MULTILINECOMMENTS_TOKEN, i);
		}

		// Remove the quotes first, so they don't get highlighted
		List<string> quotes = new List<string>();
		bool onEscape = false;
		bool onComment1 = false;
		bool onComment2 = false;
		bool inQuotes = false;
		int start = -1;
		for (int i = 0; i < content.Length; i++)
		{
			if (content[i] == '/' && !inQuotes && !onComment1)
				onComment1 = true;
			else if (content[i] == '/' && !inQuotes && onComment1)
				onComment2 = true;
			else if (content[i] == '"' && !onEscape && !onComment2)
			{
				inQuotes = true; // stops cases of: var s = "// I'm a comment";
				if (start > -1)
				{
					string quote = content.Substring(start, i - start + 1);
					if (!quotes.Contains(quote))
						quotes.Add(quote);
					start = -1;
					inQuotes = false;
				}
				else
				{
					start = i;
				}
			}
			else if (content[i] == '\\' || content[i] == '\'')
				onEscape = true;
			else if (content[i] == '\n')
			{
				onComment1 = false;
				onComment2 = false;
			}
			else
			{
				onEscape = false;
			}
		}
		
		for (int i = 0; i < quotes.Count; i++)
		{
			content = content.ReplaceToken(quotes[i], QUOTES_TOKEN, i);
		}

		// Remove the comments next, so they don't get highlighted
		regex = new Regex("(/{2,3}.+)\n", RegexOptions.Multiline);
		List<string> comments = new List<string>();
		if (regex.IsMatch(content))
		{
			foreach (Match item in regex.Matches(content))
			{
				if (!comments.Contains(item.Value + "\n"))
					comments.Add(item.Value);
			}
		}

		for (int i = 0; i < comments.Count; i++)
		{
			content = content.ReplaceToken(comments[i], COMMENTS_TOKEN, i);
		}

		// Highlight single quotes
		content = Regex.Replace(content, "('.{1,2}')", "<span class=\"quote\">$1</span>", RegexOptions.Singleline);

		// Highlight class names based on the logic: {space OR start of line OR >}{1 capital){alphanumeric}{space}
		regex = new Regex(@"((?:\s|^)[A-Z]\w+(?:\s))", RegexOptions.Singleline);
		List<string> highlightedClasses = new List<string>();
		if (regex.IsMatch(content))
		{
			foreach (Match item in regex.Matches(content))
			{
				string val = item.Groups[1].Value;
				if (!highlightedClasses.Contains(val))
					highlightedClasses.Add(val);
			}
		}

		for (int i = 0; i < highlightedClasses.Count; i++)
		{
			content = content.ReplaceWithCss(highlightedClasses[i], TypeCssClass);
		}

		// Pass 2. Doing it in N passes due to my inferior regex knowledge of back/forwardtracking.
		// This does {space or [}{1 capital){alphanumeric}{]}
		regex = new Regex(@"(?:\s|\[)([A-Z]\w+)(?:\])", RegexOptions.Singleline);
		highlightedClasses = new List<string>();
		if (regex.IsMatch(content))
		{
			foreach (Match item in regex.Matches(content))
			{
				string val = item.Groups[1].Value;
				if (!highlightedClasses.Contains(val))
					highlightedClasses.Add(val);
			}
		}

		for (int i = 0; i < highlightedClasses.Count; i++)
		{
			content = content.ReplaceWithCss(highlightedClasses[i], TypeCssClass);
		}

		// Pass 3. Generics
		regex = new Regex(@"(?:\s|\[|\()([A-Z]\w+(?:<|&lt;))", RegexOptions.Singleline);
		highlightedClasses = new List<string>();
		if (regex.IsMatch(content))
		{
			foreach (Match item in regex.Matches(content))
			{
				string val = item.Groups[1].Value;
				if (!highlightedClasses.Contains(val))
					highlightedClasses.Add(val);
			}
		}

		for (int i = 0; i < highlightedClasses.Count; i++)
		{
			string val = highlightedClasses[i];
			val = val.Replace("<", "").Replace("&lt;", "");
			content = content.ReplaceWithCss(highlightedClasses[i], val, "&lt;", TypeCssClass);
		}

		// Pass 4. new keyword with a type
		regex = new Regex(@"new\s+([A-Z]\w+)(?:\()", RegexOptions.Singleline);
		highlightedClasses = new List<string>();
		if (regex.IsMatch(content))
		{
			foreach (Match item in regex.Matches(content))
			{
				string val = item.Groups[1].Value;
				if (!highlightedClasses.Contains(val))
					highlightedClasses.Add(val);
			}
		}

		// Replace the highlighted classes
		for (int i = 0; i < highlightedClasses.Count; i++)
		{
			content = content.ReplaceWithCss(highlightedClasses[i], TypeCssClass);
		}

		// Highlight keywords
		foreach (string keyword in _keywords)
		{
			Regex regexKeyword = new Regex("(" + keyword + @")(>|&gt;|\s|\n|;|<)", RegexOptions.Singleline);
			content = regexKeyword.Replace(content, "<span class=\"keyword\">$1</span>$2");
		}

		// Shove the multiline comments back in
		for (int i = 0; i < multiLineComments.Count; i++)
		{
			content = content.ReplaceTokenWithCss(multiLineComments[i], MULTILINECOMMENTS_TOKEN, i, CommentCssClass);
		}

		// Shove the quotes back in
		for (int i = 0; i < quotes.Count; i++)
		{
			content = content.ReplaceTokenWithCss(quotes[i], QUOTES_TOKEN, i, QuotesCssClass);
		}

		// Shove the single line comments back in
		for (int i = 0; i < comments.Count; i++)
		{
			string comment = comments[i];
			// Add quotes back in
			for (int n = 0; n < quotes.Count; n++)
			{
				comment = comment.Replace(string.Format("{0}{1}{0}", QUOTES_TOKEN, n), quotes[n]);
			}
			content = content.ReplaceTokenWithCss(comment, COMMENTS_TOKEN, i, CommentCssClass);
		}
		return content;
	}
}

public static class MoreExtensions
{
	public static string ReplaceWithCss(this string content, string source, string cssClass)
	{
		return content.Replace(source, string.Format("<span class=\"{0}\">{1}</span>", cssClass, source));
	}

	public static string ReplaceWithCss(this string content, string source, string replacement, string cssClass)
	{
		return content.Replace(source, string.Format("<span class=\"{0}\">{1}</span>", cssClass, replacement));
	}

	public static string ReplaceWithCss(this string content, string source, string replacement, string suffix, string cssClass)
	{
		return content.Replace(source, string.Format("<span class=\"{0}\">{1}</span>{2}", cssClass, replacement, suffix));
	}

	public static string ReplaceTokenWithCss(this string content, string source, string token, int counter, string cssClass)
	{
		string formattedToken = String.Format("{0}{1}{0}", token, counter);
		return content.Replace(formattedToken, string.Format("<span class=\"{0}\">{1}</span>", cssClass, source));
	}

	public static string ReplaceToken(this string content, string source, string token, int counter)
	{
		string formattedToken = String.Format("{0}{1}{0}", token, counter);
		return content.Replace(source, formattedToken);
	}
}