MD5加密

public static string qswhMD5(string str)
        {
            byte[] b = System.Text.Encoding.Default.GetBytes(str);
            b = new System.Security.Cryptography.MD5CryptoServiceProvider().ComputeHash(b);
            string ret = "";
            for (int i = 0; i < b.Length; i++)
            {
                ret += b[i].ToString("x").PadLeft(2, '0');
            }
            return ret.ToUpper();
        }