避免扫描EntireRich文本框高亮显示

我正在开发一个代码编辑器，我想出了这组代码：

public class Test2 : Form {
  RichTextBox m_rtb = null;
  public static void Main() {
    Application.Run(new Test2());
  }
  public Test2() {
    Text = "Test2";
    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();
    m_rtb.TextChanged += new EventHandler(this.TextChangedEvent);
  }
  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";
  } 
  private void TextChangedEvent(object sender, EventArgs e) {
    // Calculate the starting position of the current line.
    int start = 0, end = 0;
    for (start = m_rtb.SelectionStart - 1; start > 0; start--) {
      if (m_rtb.Text[start] == ''n')  { start++; break; }
    }
    // Calculate the end position of the current line.
    for (end = m_rtb.SelectionStart; end < m_rtb.Text.Length; end++) {
      if (m_rtb.Text[end] == ''n') break;
    }
    // Extract the current line that is being edited.
    String line = m_rtb.Text.Substring(start, end - start);
    // Backup the users current selection point.
    int selectionStart = m_rtb.SelectionStart;
    int selectionLength = m_rtb.SelectionLength;
    // Split the line into tokens.
    Regex r = new Regex("([ ''t{}();])");
    string [] tokens = r.Split(line);
    int index = start;
    foreach (string token in tokens) {
      // Set the token's default color and font.
      m_rtb.SelectionStart = index;
      m_rtb.SelectionLength = token.Length;
      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 length = line.Length - (index - start);
        string commentText = m_rtb.Text.Substring(index, length);
        m_rtb.SelectionStart = index;
        m_rtb.SelectionLength = length;
        m_rtb.SelectionColor = Color.LightGreen;
        m_rtb.SelectionFont = new Font("Courier New", 10, FontStyle.Regular);
        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;
        }
      }
      index += token.Length;
    }
    // Restore the users current selection point.    
    m_rtb.SelectionStart = selectionStart;
    m_rtb.SelectionLength = selectionLength;  
  } 
}

问题是每次我按空格键或键入时，整个代码编辑器都会像搜索突出显示的内容一样不断扫描，我觉得这有点烦人。。。

所以我只想寻求可能的解决方案。。。以避免像扫描下一步要突出显示的内容那样突出显示整个richtextbox。

提前感谢您的帮助！更强大！