using System.Text.RegularExpressions;
The second step is to detect a URL:

Regex urlregex = new Regex(@"(http:\/\/([\w.]+\/?)\S*)",
   RegexOptions.IgnoreCase|RegexOptions.Compiled);

Here is how to detect an e-mail address:

Regex emailregex = new 
Regex(@"([a-zA-Z_0-9.-]+\@[a-zA-Z_0-9.-]+\.\w+)",
   RegexOptions.IgnoreCase|RegexOptions.Compiled);



private void Button1_Click(object sender, System.EventArgs 
e)
{
   string strContent = InputTextBox.Text;
   Regex urlregex = new Regex(@"(http:\/\/([\w.]+\/?)\S*)",
                    RegexOptions.IgnoreCase| 
RegexOptions.Compiled);
   strContent = urlregex.Replace(strContent,
                "");
   Regex emailregex = new 
Regex(@"([a-zA-Z_0-9.-]+\@[a-zA-Z_0-9.-]+\.\w+)",
      RegexOptions.IgnoreCase| RegexOptions.Compiled);
   strContent = emailregex.Replace(strContent, "");
   lbContent.Text += ""+strContent;
}