public string CalculateMD5Hash(string input)
{
  // step 1, calculate MD5 hash from input
  MD5 md5 = System.Security.Cryptography.MD5.Create();
  byte[] inputBytes = System.Text.Encoding.ASCII.GetBytes(input);
  byte[] hash = md5.ComputeHash(inputBytes);
  // step 2, convert byte array to hex string
  StringBuilder sb = new StringBuilder();
  for (int i = 0; i < hash.Length; i++)
  { sb.Append(hash[i].ToString(“X2”));
  }
  return sb.ToString();
}

public static String md5(String s)
{
  MD5 md5 = new MD5CryptoServiceProvider();
  byte[] bytes = System.Text.Encoding.UTF8.GetBytes(s);
  bytes = md5.ComputeHash(bytes);
  md5.Clear();

  string ret = "";
  for (int i = 0; i < bytes.Length; i++)
  {
    ret += Convert.ToString(bytes[i], 16).PadLeft(2, '0');
  }
  return ret.PadLeft(32, '0');
}