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。

posted @ 2011-04-15 10:37  程兴亮  阅读(3564)  评论(15编辑  收藏