Wp7客户端与Webservice的数据传输，json的序列化与反序列化

public class JsonHelper
{
public static string JsonSerializer<T>(T t)
{
DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(T));
MemoryStream ms = new MemoryStream();
ser.WriteObject(ms, t);
string jsonString = Encoding.UTF8.GetString(ms.ToArray());
ms.Close();
return jsonString;
}
public static T JsonDeserialize<T>(string jsonString)
{
DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(T));
MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(jsonString));
T obj = (T)ser.ReadObject(ms);
return obj;
}
}

public class WeatherInfo
{
public string CityName { get; set; }
public string Date { get; set; }
}

[WebMethod(Description = "返回信息")]
public string getJson(String city)
{
WeatherInfo weather = new WeatherInfo();
weather.CityName = city;
weather.Date = Date.Now.ToString();
string jsonString = JsonHelper.JsonSerializer<WeatherInfo>(weather);
return jsonString;
}

public void GetForecast(string city)
{
WebClient client = new WebClient();
client.OpenReadAsync(new Uri("http://localhost/Weather.asmx/getJson?city=" + city
+ "&time=" + DateTime.Now.ToString("yyyyMMddHHmmss"),UriKind.RelativeOrAbsolute));
client.OpenReadCompleted += new OpenReadCompletedEventHandler(client_OpenReadCompleted);
}

void client_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
try
{
XElement xmlWeather;
xmlWeather = XElement.Load(e.Result);
WeatherInfo weatherInfo = new WeatherInfo();

weatherInfo = JsonHelper.JsonDeserialize<WeatherInfo>(xmlWeather.Value);

//Debug.WriteLine(weatherInfo.CityName);

}
catch (Exception)
{
Deployment.Current.Dispatcher.BeginInvoke(() =>
{
MessageBox.Show("数据获取出错。");
});
}
}