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。
