将字符串中指定字符替换成其他不同字符

public static int i = 0;
private void dd()
{
string sone, stwo;
sone = "afasf<span style="color:red" mce_style="color:red">{A}</span>asd<span style="color:red" mce_style="color:red">{A}</span>fdd<span style="color:red" mce_style="color:red">{A}</span>ddd<span style="color:red" mce_style="color:red">{A}</span>----<span style="color:red" mce_style="color:red">{A}</span>asfasdfasd<span style="color:red" mce_style="color:red">{A}</span>54646<span style="color:red" mce_style="color:red">{A}</span>";
stwo = "{A}";
Regex r = new Regex(stwo);
MatchEvaluator myEvaluator = new MatchEvaluator(ReplaceCC);
Response.Write("原 字 符  串:" + sone+"<br/>");
sone = r.Replace(sone, myEvaluator);
Response.Write("替换后字符串:"+sone);
}
public string ReplaceCC(Match m)
{
List<string> l = new List<string>();
l.Add("我");
l.Add("是");
l.Add("中");
l.Add("国");
l.Add("人");
if (i < l.Count)
{
i++;
}
else
{
i = 1;
}
return l[i-1].ToString();
}