c# 解析JSON的几种办法
欲成为海洋大师，必知晓海中每一滴水的真名。
刚开始只是想找一个转换JSON数组的方法，结果在MSDN翻到一大把。
搜索过程中免不了碰到一大堆名词：WCF => DataContract => DataMember => DataContractJsonSerializer，然后就是不停的引入命名空间。
这一段经历，立即让我就联想到了上面引用的这句存在于某小说里面巫师的话语。静态语言真有点令人抓狂，不停的做准备，然后才可能开始工作。
对比
| 主要类 | 命名空间 | 限制 | 内建LINQ支持 |
|---|---|---|---|
| DataContractJsonSerializer | System.Runtime.Serialization.Json | 通用 | 否 |
| JavaScriptSerializer | System.Web.Script.Serialization | 只能在Web环境使用 | 否 |
| JsonArray、JsonObject、JsonValue | System.Json | 只能在Silverlight中使用 | 是 |
| JsonConvert、JArray、JObject、JValue、JProperty | Newtonsoft.Json | 通用 | 是 |
准备数据
实体类：
[DataContract]
public class Person
{
[DataMember(Order = 0, IsRequired = true)]
public string Name { get; set; }
[DataMember(Order = 1)]
public int Age { get; set; }
[DataMember(Order = 2)]
public bool Alive { get; set; }
[DataMember(Order = 3)]
public string[] FavoriteFilms { get; set; }
[DataMember(Order = 4)]
public Person Child { get; set; }
}
定义：
Action<object> log = o => Console.WriteLine(o);
Func<int, int, int> add = (x, y) => x + y;
var p1 = new Person {
Age = 12,
Alive = true,
Name = "lj",
FavoriteFilms = new[] { "Up", "Avatar" }
};
var p2 = new Person() { Age = 28, Name = "cy", Child = p1 };
使用DataContractJsonSerializer
帮助类：
// using System.Runtime.Serialization.Json;
/// <summary>
/// 解析JSON，仿Javascript风格
/// </summary>
public static class JSON
{
public static T parse<T>(string jsonString)
{
using (var ms = new MemoryStream(Encoding.UTF8.GetBytes(jsonString)))
{
return (T)new DataContractJsonSerializer(typeof(T)).ReadObject(ms);
}
}
public static string stringify(object jsonObject)
{
using (var ms = new MemoryStream())
{
new DataContractJsonSerializer(jsonObject.GetType()).WriteObject(ms, jsonObject);
return Encoding.UTF8.GetString(ms.ToArray());
}
}
}
用法：
// 序列化
var jsonString = JSON.stringify(new[] { p1, p2 });
log(jsonString == JSON.stringify(new List<Person>() { p1, p2 })); //true
log(jsonString);
// 反序列化，泛型集合
JSON.parse<List<Person>>(jsonString);
// 数组转换
JSON.parse<Person[]>(jsonString);
输出：
[{"Name":"lj","Age":12,"Alive":true,"FavoriteFilms":["Up","Avatar"],"Child":null
},{"Name":"cy","Age":28,"Alive":false,"FavoriteFilms":null,"Child":{"Name":"lj",
"Age":12,"Alive":true,"FavoriteFilms":["Up","Avatar"],"Child":null}}]
使用JavaScriptSerializer
// using System.Web.Script.Serialization;
var jser = new JavaScriptSerializer();
var json = jser.Serialize(new List<Person>() { p1, p2 });
var persons = jser.Deserialize<List<Person>>(json);
使用Silverlight
// using System.Json
var css = "{ \"#header\" : {background:\"red\"}, layout : [5,4,1],color:\"cyan\" }";
var style = JsonObject.Parse(css) as JsonObject;
(
from s in style
where s.Key == "color"
select (string)s.Value
).First().ToString();
// "cyan"
// 更多操作
style["layout"][0] = 22;
var hd = style["#header"];
style["body>div+p"] = hd;
style.Remove("#header");
var bd = new JsonObject();
bd["border"] = "1px solid cyan";
style["body>div+p"]["#meta"] = bd;
style.ToString();
// {"layout":[22,4,1],"color":"cyan","body>div+p":{"background":"red","#meta":{"border":"1px solid cyan"}}}
使用JSON.NET
// using Newtonsoft.Json;
var json = JsonConvert.SerializeObject(new[] { p1, p2 });
var persons = JsonConvert.DeserializeObject<List<Person>>(json);
var ja = JArray.Parse(jsonString);
log(ja); //注意，格式化过的输出
输出：
[
{
"Name": "lj",
"Age": 12,
"Alive": true,
"FavoriteFilms": [
"Up",
"Avatar"
],
"Child": null
},
{
"Name": "cy",
"Age": 28,
"Alive": false,
"FavoriteFilms": null,
"Child": {
"Name": "lj",
"Age": 12,
"Alive": true,
"FavoriteFilms": [
"Up",
"Avatar"
],
"Child": null
}
}
]
LINQ：
var ageCount = ja.Select(j => (int)j["Age"]).Aggregate(add);
var q = from j in ja
where !j["Name"].Value<string>().Equals("lj")
select (int)j["Age"];
log(q.Aggregate(add) == ageCount); //false
其他：
// 与Linq to XML 相似的嵌套构造函数：
var jo = new JObject(
new JProperty("age", persons.Select( p => p.Age)),
new JProperty("funny", true),
new JProperty("array", new JArray(new[] { 2, 4, 1 }))
);
log(jo);
// JObject 操作
var css = "{ \"#header\" : {background:\"red\"}, layout : [5,4,1] }";
var style = JObject.Parse(css);
var bd = new JObject();
bd["color"] = "1px solid cyan";
style["border"] = bd;
var hd = style["#header"];
style["body>div+p"] = hd;
hd.Parent.Remove();
style["layout"][0] = 22;
log(style);
输出：
{
"age": [
12,
28
],
"funny": true,
"array": [
2,
4,
1
]
}
{
"layout": [
22,
4,
1
],
"border": {
"color": "1px solid cyan"
},
"body>div+p": {
"background": "red"
}
}