关于关键字替换的功能，求教，附下代码

关于关键字替换的功能，求教，附上代码
原文内容：我们都是百度的人啊怎么是goolge的人呢？
 被替换后： <a href=' Google.html'><a href=' 百度.html'><a href=' a.html'>我们</a></a></a>都是<a href=' Google.html'><a href=' <a href=' a.html'>百度</a>.html'>百度</a></a>的人啊怎么是goolge的人呢？
实际应该是：我们都是<a herf=百度.html>百度</a>的人啊怎么是<a herf=goolge.html>goolge</a>的人呢？

C# code

private bool DoAdd()        {            Regex reg = new Regex(@"(?:^|(?<!<(?:a|pre)\b(?>[^<>]*))>)(?>[^<>]*)(?:<|$)", RegexOptions.IgnoreCase | RegexOptions.Compiled);            string result2 = reg.Replace(txtContent.Value, RegReplace);            richTextBox2.Text = result2; .......} List<string> tags = new List<string>(new string[] { "Google", "百度", "a"}); List<string> tagssa = new List<string>(new string[] { "Google.html", "百度.html", "a.html" });int index = -1;string temp = string.Empty;List<string> list = new List<string>();List<string> list2 = new List<string>();private string RegReplace(Match m){    temp = m.Value;    foreach (string tag in tags)    {        foreach(string tag2 in tagssa)        {        index = temp.IndexOf(tag);        if (index > -1)        {            list.Add(tag);            list2.Add(tag2);            temp = temp.Substring(0, index) + "<a href=' " + tag2 + "'>" + tag + "</a>" + temp.Substring(index + tag.Length);        }         }    }    foreach (string s in list)    {        tags.Remove(s);    }    foreach (string s2  in list2)    {        tags.Remove(s2);    }    list.Clear();    list2.Clear();    return temp;}

C# code

 string temp = @"我们都是百度的人啊怎么是google的人呢？";                Dictionary<string, string> dic = new Dictionary<string, string>() {                     {"Google","Google.html"},                    {"百度","百度.html"},                    {"a","a.html"}                };                                foreach (var item in dic)                {                    string pattern_dic = @"(?i)(?<![</])"+item.Key;                    temp = Regex.Replace(temp, pattern_dic, a => {                        return @"<a href='" + item.Value + "'>" + a.Value + "</a>";                    });                }                //我们都是<a href='百度.html'>百度</a>的人啊怎么是<a href='Google.html'>google</a>的人呢？