MatchEvaluator应用 替换

 public static void MatchEvaluator()
        {
            string str = "<You're angle & evil>";
            string pattern = "'|&|<|>";
            Regex regex = new Regex(pattern);
            MatchEvaluator evaluator = new MatchEvaluator(ConvertToXML);
            Console.WriteLine(regex.Replace(str, evaluator));
            Console.Read();
            //理解：把符合正式表达式的字符串再通过MatchEvaluator中的ConvertToXML二次处理


        }
        public static string ConvertToXML(Match m)
        {
            switch (m.Value)
            {
                case "'":
                    return "&apos";
                case "&":
                    return "&amp";
                case "<":
                    return "&lt";
                case ">":
                    return "&gt";
                default:
                    return "";
            }
        }