在RichTextBox中对关键字进行高亮显示

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Text.RegularExpressions;

namespace HighLight
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void HighLightText()
        {
            string[] keywords =   {"select","distinct","from","where","order","by","group","null"};
            string[] functions =   { "isnull", "count", "sum" };
            string[] strings =   { @"'((.|\n)*?)'" };
            string[] whiteSpace =   { "\t", "\n", "   " };

            rtbSql.SelectAll();
            rtbSql.SelectionColor = Color.Black;

            HighLightText(keywords, Color.Blue);
            HighLightText(functions, Color.Magenta);
            HighLightText(strings, Color.Red);
            HighLightText(whiteSpace, Color.Black);
        }

        private void HighLightText(string[] wordList, Color color)
        {
            foreach (string word in wordList)
            {
                Regex r = new Regex(word, RegexOptions.IgnoreCase);

                foreach (Match m in r.Matches(rtbSql.Text))
                {
                    rtbSql.Select(m.Index, m.Length);
                    rtbSql.SelectionColor = color;
                }
            }
        }   

        private void btnHighLight_Click(object sender, EventArgs e)
        {
            HighLightText();
        }
    }
}