using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.Text.RegularExpressions;
namespace ConsoleApplication3
{
 class Program
 {
  static void Main(string[] args)
  {
   string s = "例如：http://www.asd.com";
   Regex re = new Regex(@"(?<url>http(s)?://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?)");
   MatchCollection mc = re.Matches(s);
   foreach (Match m in mc)
   {
    s=s.Replace(m.Result("${url}"), String.Format("<a href='{0}'>{0}</a>", m.Result("${url}")));
   }
   Console.WriteLine(s);
  }
 }
}