using System;
using System.Windows.Forms;
using System.Drawing;
using System.Text.RegularExpressions;

public class Test : Form
{
    RichTextBox m_rtb = null;
    public static void Main()
    {
        Application.Run(new Test());
    }
    public Test()
    {
        Text = "Test";
        ClientSize = new Size(400, 400);
        m_rtb = new RichTextBox();
        m_rtb.Multiline = true;
        m_rtb.WordWrap = false;
        m_rtb.AcceptsTab = true;
        m_rtb.ScrollBars = RichTextBoxScrollBars.ForcedBoth;
        m_rtb.Dock = DockStyle.Fill;
        m_rtb.SelectionFont = new Font("Courier New", 10, FontStyle.Regular);
        m_rtb.SelectionColor = Color.Black;
        Controls.Add(m_rtb);
        Parse();
    }
    void Parse()
    {
        String inputLanguage =
          "// Comment.\n" +
          "using System;\n" + "\n" +
          "public class Stuff : Form { \n" +
          "  public static void Main(String args) {\n" +
          "  }\n" +
          "}\n";

        // Foreach line in input,
        // identify key words and format them when adding to the rich text box.
        Regex r = new Regex("\\n");
        String[] lines = r.Split(inputLanguage);
        foreach (string l in lines)
        {
            ParseLine(l);
        }
    }
    void ParseLine(string line)
    {
        Regex r = new Regex("([ \\t{}();])");
        String[] tokens = r.Split(line);

        foreach (string token in tokens)
        {
            // Set the token's default color and font.
            m_rtb.SelectionColor = Color.Black;
            m_rtb.SelectionFont = new Font("Courier New", 10, FontStyle.Regular);

            // Check for a comment.
            if (token == "//" || token.StartsWith("//"))
            {
                // Find the start of the comment and then extract the whole comment.
                int index = line.IndexOf("//");
                string comment = line.Substring(index, line.Length - index);
                m_rtb.SelectionColor = Color.LightGreen;
                m_rtb.SelectionFont = new Font("Courier New", 10, FontStyle.Regular);
                m_rtb.SelectedText = comment;
                break;
            }

            // Check whether the token is a keyword. 
            String[] keywords = { "public", "void", "using", "static", "class" };
            for (int i = 0; i < keywords.Length; i++)
            {
                if (keywords[i] == token)
                {
                    // Apply alternative color and font to highlight keyword.
                    m_rtb.SelectionColor = Color.Blue;
                    m_rtb.SelectionFont = new Font("Courier New", 10, FontStyle.Bold);
                    break;
                }
            }
            m_rtb.SelectedText = token;
        }
        m_rtb.SelectedText = "\n";
    }
}