介绍一下今天的实例，实例是调用一个汇率API（http://xurrency.com/）来实现货币转换，该API返回的就是JSON数据。但是免费用户使用该API有每天使用10次的限制，所以可能您在测试的时候返回错误，是因为达到了限制。 解析与生成JSON需要System.Runtime.Serialization.Json命名空间，但得先从菜单添加引用”System.Runtime.Serialization”。Windows Phone 7上稍有不同，参考：Windows Phone 7解析Json实例 货币转换小程序源码下载 代码：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.Serialization.Json;
using System.Runtime.Serialization;
using System.IO;
using System.Net;
namespace Json
{
class Program
{
[DataContract(Namespace = "http://www.pocketdigi.com")]
public class Currency
{
[DataMember(Order = 0)]
public result result { get; set; }
[DataMember(Order = 1)]
public int code { get; set; }
[DataMember(Order = 2)]
public string status { get; set; }
}
[DataContract(Namespace = "http://www.pocketdigi.com")]
public class result
{
[DataMember(Order = 0)]
public string updated_at { get; set; }
[DataMember(Order = 1)]
public float value { get; set; }
[DataMember(Order = 2)]
public string target { get; set; }
[DataMember(Order = 3)]
public string Base { get; set; }
//返回的是base,但因base是c#关键字，这里用Base代替，在下面拿到api返回数据时也替换成Base
}
//API反回的结果形似:{"result":{"updated_at":"2011-09-21T09:04:00Z","value":637.92,"target":"cny","base":"usd"},"code":0,"status":"ok"}
//定义两个类，一个为Currency,包括返回的所有信息，一个为result类，包括updated_at,value,target,base
static void Main(string[] args)
{
var currency = new Currency()
{
result = new result() { updated_at = "2011-09-14T14:03:00Z", value = 639.478f, target = "CNY", Base = "USD" },
code = 0,
status = "OK"
};
//通过传入参数实例化一个Currency类
var serializer = new DataContractJsonSerializer(typeof(Currency));
var stream = new MemoryStream();
serializer.WriteObject(stream, currency);
//序列化，并写入到stream
byte[] dataBytes = new byte[stream.Length];
stream.Position = 0;
stream.Read(dataBytes, 0, (int)stream.Length);
string dataString = Encoding.UTF8.GetString(dataBytes);
//从stream读入到string,即生成JSON
Console.WriteLine("JSON string is:");
Console.WriteLine(dataString);
//string s="{\"result\":{\"updated_at\":\"2011-09-14T14:03:00Z\",\"value\":639.47,\"target\":\"cny\",\"Base\":\"usd\"},\"code\":0,\"status\":\"ok\"}";
WebClient webClient = new WebClient();
string s = webClient.DownloadString("http://xurrency.com/api/usd/cny/100");
//下载API返回数据，因为API每天每IP限制调用10次，所以超过10次会返回错误
//api调用方法 http://xurrency.com/api/原货币小写代码/目标货币小写代码/数额
s = s.Replace("base", "Base");
//因为base是C#关键字， 所以替换一下
Console.WriteLine(s);
//输出API返回字符串
var mStream = new MemoryStream(Encoding.UTF8.GetBytes(s));
DataContractJsonSerializer serializer2 = new DataContractJsonSerializer(typeof(Currency));
Currency readCurrency = (Currency)serializer2.ReadObject(mStream);
//反序列化成Currency类实例
Console.WriteLine(readCurrency.result.value);
//读取value值
}
}
}