正则匹配连接

上码：

string[] imgtag = { ".gif", ".jpg", ".png", ".jpeg" };
string tpllink = "<a target=\"_blank\" style=\"color:#e25252;text-decoration: underline;\" href='{0}'>{1}</a>";
Regex re = new Regex(@"((http|https)://)?(([a-zA-Z0-9\._-]+\.[a-zA-Z]{2,6})|([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}))(:[0-9]{1,4})*(/[^<|^>]*)?");
MatchCollection matchCollection = re.Matches(txtmsg);
HashSet<string> urlKeys = new HashSet<string>();
foreach (Match m in matchCollection)
{
if (imgtag.Any(x => m.Value.Contains(x)))
{
continue;
}

if (urlKeys.Add(m.Value))
{
txtmsg = txtmsg.Replace(m.Value, String.Format(tpllink, m.Value.Contains("http://") ? m.Value : "http://" + m.Value, m.Value));
}
}