string myInputString = "";
            string mAppID = "";
            string mySecurityID = "";
            int mySalt = 0;
           
            //mAppIDmyInputStringmySaltmySecurityID
            StringBuilder mySignString = new StringBuilder();
            string myMd5Result = string.Empty;
            //1.拼接字符,为了生成sign
            mySignString.Append(mAppID);
            mySignString.Append(myInputString);
            mySignString.Append(mySalt);
            mySignString.Append(mySecurityID);

            //2.通过md5获取sign
            byte[] sourceMd5Byte = Encoding.Default.GetBytes(mySignString.ToString());
            MD5 md5 = new MD5CryptoServiceProvider();
            byte[] destMd5Byte = md5.ComputeHash(sourceMd5Byte);
            myMd5Result = BitConverter.ToString(destMd5Byte).Replace("-", "");
            myMd5Result = myMd5Result.ToLower();

            //3.获取web翻译的json结果
            WebClient client = new WebClient();
            string url = string.Format
           ("http://api.fanyi.baidu.com/api/trans/vip/translate?q={0}&from=en&to=zh&appid={1}&salt={2}&sign={3}", myInputString, mAppID, mySalt, myMd5Result);
            byte[] buffer = client.DownloadData(url);
            string result = Encoding.UTF8.GetString(buffer);
            StringReader sr = new StringReader(result);
            //解析数据
            JsonTextReader jsonReader = new JsonTextReader(sr);
            JsonSerializer serializer = new JsonSerializer();
            var r = serializer.Deserialize<TransObj>(jsonReader);
            txtResult.Text = r.trans_result[0].dst;

    public class TransObj
    {
        public string from { get; set; }
        public string to { get; set; }
        public List<TransResult> trans_result { get; set; }
    }

    public class TransResult
    {
        public string src { get; set; }
        public string dst { get; set; }
    }