Best MD5 String Function

using System.Security.Cryptography;
    static string MD5Str(string raw)
    {
      MD5 md5serv = MD5CryptoServiceProvider.Create();
      byte[] hash;
      StringBuilder stringbuff = new StringBuilder();
      ASCIIEncoding asciienc = new ASCIIEncoding();
      byte[] buffer = asciienc.GetBytes(raw);
      hash = md5serv.ComputeHash(buffer);
      foreach (byte b in hash)
      {
        stringbuff.Append(b.ToString("x2"));
      }
      return stringbuff.ToString();
    }