static public string GetMd5Sum(string str)
{
 Encoder enc = System.Text.Encoding.Unicode.GetEncoder();
 byte[] unicodeText = new byte[str.Length * 2];
enc.GetBytes(str.ToCharArray(), 0, str.Length, unicodeText, 0, true);
 MD5 md5 = new MD5CryptoServiceProvider();
 byte[] result = md5.ComputeHash(unicodeText);
 StringBuilder sb = new StringBuilder();
 for (int i=0;i<result.length;i++){
  sb.Append(result[i].ToString("X2"));
 }
 return sb.ToString();
}