How to grab links from an HTML page

protected void Button1_Click(object sender, EventArgs e)
   {
       string url = TextBox1.Text;
       WebClient wc = new WebClient();

       string html = wc.DownloadString(url);

       ArrayList linkCount = CollectLinks(html);

       StringBuilder sb = new StringBuilder();
       int c = 1;
       sb.Append("<table> <tr>  <td style="padding-right:40px;">   #   </td>   <td>  URL </td> </tr> ");
       foreach (var item in linkCount)
       {
           sb.Append(" <tr>  <td>    " + c.ToString() + "   </td>   <td>  " + item.ToString() + " </td> </tr>");
           c++;
       }
       sb.Append("</table>");

       lblResult.Text = sb.ToString();
   }

   public ArrayList CollectLinks(string strSource)
   {
       ArrayList ar = new ArrayList();
       try
       {
           Regex r1 = new Regex("((http://|www\\.)([A-Z0-9.-:]{1,})\\.[0-9A-Z?;~:&+%#=\\-_\\./]{2,})", RegexOptions.Compiled | RegexOptions.IgnoreCase);
           MatchCollection mc = r1.Matches(strSource);
           foreach (Match m in mc)
           {
               ar.Add(m);
           }
       }
       catch (Exception exp)
       {

       }

       return ar;
   }