.NET(C#) Json.Net(newtonsoft)使用LINQ查询JSON数据

1、通过属性名或集合索引获取值将一个值从LINQ转换为JSON的最简单方法是在JObject/JArray上使用Item[Object]索引，然后将返回的JValue转换为您想要的类型。string json = @"{ 'channel': { 'title': 'James Newt

1、通过属性名或集合索引获取值

将一个值从LINQ转换为JSON的最简单方法是在JObject/JArray上使用Item[Object]索引，然后将返回的JValue转换为您想要的类型。

string json = @"{  'channel': {    'title': 'James Newton-King',    'link': 'http://james.newtonking.com',    'description': 'James Newton-King\'s blog.',    'item': [      {        'title': 'Json.NET 1.3 + New license + Now on CodePlex',        'description': 'Announcing the release of Json.NET 1.3, the MIT license and the source on CodePlex',        'link': 'http://james.newtonking.com/projects/json-net.aspx',        'categories': [          'Json.NET',          'CodePlex'        ]      },      {        'title': 'LINQ to JSON beta',        'description': 'Announcing LINQ to JSON',        'link': 'http://james.newtonking.com/projects/json-net.aspx',        'categories': [          'Json.NET',          'LINQ'        ]      }    ]  }}";JObject rss = JObject.Parse(json);string rssTitle = (string)rss["channel"]["title"];// James Newton-Kingstring itemTitle = (string)rss["channel"]["item"][0]["title"];// Json.NET 1.3 + New license + Now on CodePlexJArray categories = (JArray)rss["channel"]["item"][0]["categories"];// ["Json.NET", "CodePlex"]IList categoriesText = categories.Select(c => (string)c).ToList();// Json.NET// CodePlex

2、用LINQ查询

还可以使用LINQ查询JObject/JArray。Children()以IEnumerable的形式返回JObject/JArray的子值，然后可以使用Where/OrderBy/Select LINQ操作符查询这些子值。

Note:

Children()返回令牌的所有子元素。如果是JObject，它将返回要处理的属性集合;如果是JArray，则会得到数组值的集合。

var postTitles =    from p in rss["channel"]["item"]    select (string)p["title"];foreach (var item in postTitles){    Console.WriteLine(item);}//LINQ to JSON beta//Json.NET 1.3 + New license + Now on CodePlexvar categories =    from c in rss["channel"]["item"].SelectMany(i => i["categories"]).Values()    group c by c    into g    orderby g.Count() descending    select new { Category = g.Key, Count = g.Count() };foreach (var c in categories){    Console.WriteLine(c.Category + " - Count: " + c.Count);}//Json.NET - Count: 2//LINQ - Count: 1//CodePlex - Count: 1

LINQ to JSON还可用于手动将JSON转换为.NET对象

public class Shortie
{
    public string Original { get; set; }
    public string Shortened { get; set; }
    public string Short { get; set; }
    public ShortieException Error { get; set; }
}
public class ShortieException
{
    public int Code { get; set; }
    public string ErrorMessage { get; set; }
}

当您处理与.NET对象不匹配的JSON时，在.NET对象之间手动序列化和反序列化非常有用

string jsonText = @"{  'short': {    'original': 'http://www.foo.com/',    'short': 'krehqk',    'error': {      'code': 0,      'msg': 'No action taken'    }  }}";JObject json = JObject.Parse(jsonText);Shortie shortie = new Shortie{    Original = (string)json["short"]["original"],    Short = (string)json["short"]["short"],    Error = new ShortieException    {        Code = (int)json["short"]["error"]["code"],        ErrorMessage = (string)json["short"]["error"]["msg"]    }};Console.WriteLine(shortie.Original);// http://www.foo.com/Console.WriteLine(shortie.Error.ErrorMessage);// No action taken