Requires Newtonsoft.Json package

GoogleTranslator.cs

 public class GoogleTranslator
  {
        private readonly string _outLanguage;
        private readonly string _inLanguage;

        public GoogleTranslator()
        {
            _inLanguage = "en";
            _outLanguage = "de";
        }

        public async Task<string> Translate(string textToTranslate)
        {
            var httpClient = new WebClient() { Encoding = Encoding.Default };
            var urlToGet = BuildUrl(textToTranslate);

            var result = await httpClient.DownloadStringTaskAsync(urlToGet);

            dynamic json = JObject.Parse(result);

            return json.sentences[0].trans.Value;
        }

        private string BuildUrl(string textToTranslate)
        {
            const string urlFormat = "http://translate.google.ru/translate_a/t?client=x&text={0}&sl={1}&tl={2}";

            return String.Format(urlFormat, textToTranslate, _inLanguage, _outLanguage);
        }
}