Silverlight实用窍门系列：38.Silverlight读取服务器端格式化的Json数据【附带实例源码】

        Json数据是一种轻量级的数据交换格式，它的传输效率比XML更高，在Silverlight的应用起来可以让Silverlight获取数据速度增快，减少传输的字符数量。在本节将用一个实例来讲解如何将一个类序列化为Json数据并且传输到Silverlight端。

        实现原理：在服务器端新建一个一般处理程序页面“GetJson.ashx”，使用DataContractJsonSerializer类的WriteObject()函数来将类序列化为Json数据集合，然后再Silverlight端通过DataContractJsonSerializer类的ReadObject()函数来将Json数据还原为类。当然在Silverlight端我们使用WebRequest来下载数据。

        首先我们新建一个新的Silverlight应用程序，然后再服务器端和Silverlight端同时添加两个类City.cs（有数个属性）和Citys.cs（有一个属性为City类的List集合）。

    public class City
    {
        private string _CityName;
        private string _CityNum;
        private string _Provence;

        public string Provence
        {
            get { return _Provence; }
            set { _Provence = value; }
        }
        public string CityNum
        {
            get { return _CityNum; }
            set { _CityNum = value; }
        }
        public string CityName
        {
            get { return _CityName; }
            set { _CityName = value; }
        }
    }
    public class Citys
    {
        private List<City> _CityList;

        public List<City> CityList
        {
            get { return _CityList; }
            set { _CityList = value; }
        }
    }

        然后我们在服务器端新建一个一般处理程序页面“GetJson.ashx”，然后添加以下代码以实例化多个城市对象，然后转回为Json数据。注意在这里我们需要单独引入System.Runtime.Serialization.dll;

   /// <summary>
    /// GetJson 的摘要说明
    /// </summary>
    public class GetJson : IHttpHandler
    {
        
        public void ProcessRequest(HttpContext context)
        {
            //步骤一
            //将类Citys格式化为Json字符串
            string JsonString = ToJsonString(GetCitys());
            context.Response.ContentType = "text/plain";
            context.Response.Write(JsonString);
        }

        private Citys GetCitys()
        {
            //实例化字符数据组
            Citys citys = new Citys();
            citys.CityList = new List<City>() { 
            new City(){ CityName="成都", CityNum="028", Provence="四川"},
            new City(){ CityName="昆明", CityNum="028", Provence="云南"},
            new City(){ CityName="广州", CityNum="028", Provence="广东"},
            new City(){ CityName="上海", CityNum="028", Provence="上海"},
            new City(){ CityName="重庆", CityNum="028", Provence="重庆"}
            };
            return citys;
        }
        // 将一个Object类序列化为Json字符串
        public string ToJsonString(object ToJsonObject)
        {
            using (MemoryStream ms = new MemoryStream())
            {
                DataContractJsonSerializer serializer =
                    new DataContractJsonSerializer(ToJsonObject.GetType());
                serializer.WriteObject(ms, ToJsonObject);
                StringBuilder sb = new StringBuilder();
                sb.Append(Encoding.UTF8.GetString(ms.ToArray()));
                return sb.ToString();
            }
        }
        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }

        运行GetJson.ashx页面我们可以得到类格式化为Json之后的字符如下：

{"CityList":[{"CityName":"成都","CityNum":"028","Provence":"四川"},
{"CityName":"昆明","CityNum":"028","Provence":"云南"},
{"CityName":"广州","CityNum":"028","Provence":"广东"},
{"CityName":"上海","CityNum":"028","Provence":"上海"},
{"CityName":"重庆","CityNum":"028","Provence":"重庆"}]}

        在Silverlight端首先需要引入System.ServiceModel.Web.dll和System.Runtime.Serialization.dll,然后再敲入下面代码以调用一般应用程序页面得到的字符串，并且反序列化为类。

public MainPage()
{
    InitializeComponent();
    //步骤二
    //调用http://localhost:2598/GetJson.ashx获取到Json数据流
    Uri endpoint = new Uri("http://localhost:2598/GetJson.ashx");
    WebRequest request = WebRequest.Create(endpoint);
    request.Method = "POST";
    request.ContentType = "application/x-www-form-urlencoded";
    request.BeginGetResponse(new AsyncCallback(ResponseReady), request);

}
void ResponseReady(IAsyncResult asyncResult)
{
    WebRequest request = asyncResult.AsyncState as WebRequest;
    WebResponse response = request.EndGetResponse(asyncResult);
    //步骤三
    //调用UI线程更新DataGrid
        this.dataGrid1.Dispatcher.BeginInvoke(()=>{
            this.dataGrid1.ItemsSource = 
                (Deserialize<Citys>(response.GetResponseStream()) as Citys).CityList;
        });
}
// 将Json字符流反序列化为对象 
public static T Deserialize<T>(Stream stream)
{
        DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(T));
        return (T)serializer.ReadObject(stream);
} 

       本实例采用VS2010+Silverlight 4.0,如需源码请点击 SLLinkJson.rar 下载。