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。