今天小编给大家分享一下C#中的Linq to JSON操作实例分析的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。
Linq to JSON是用来操作JSON对象的，可以用于快速查询、修改和创建JSON对象。
当JSON对象内容比较复杂，而我们仅仅需要其中的一小部分数据时，可以考虑使用Linq to JSON来读取和修改部分的数据而非反序列化全部。
在进行Linq to JSON之前,首先要了解一下用于操作Linq to JSON的类.
| 类名 | 说明 |
|---|---|
| JObject | 用于操作JSON对象 |
| JArray | 用语操作JSON数组 |
| JValue | 表示数组中的值 |
| JProperty | 表示对象中的属性,以"key/value"形式 |
| JToken | 用于存放Linq to JSON查询后的结果 |
一、创建JObject and JArrary实例
1、手动创建JSON
设置值和一次创建一个对象或数组可以让您完全控制，但是它比其他选项更冗长。
1、创建JSON对象，JObject
JObject staff = new JObject();staff.Add(new JProperty("Name", "Jack"));staff.Add(new JProperty("Age", 33));staff.Add(new JProperty("Department", "Personnel Department"));staff.Add(new JProperty("Leader", new JObject(new JProperty("Name", "Tom"), new JProperty("Age", 44), new JProperty("Department", "Personnel Department"))));Console.WriteLine(staff.ToString());//返回//{// "Name": "Jack",// "Age": 33,// "Department": "Personnel Department",// "Leader": {// "Name": "Tom",// "Age": 44,// "Department": "Personnel Department"// }//}2、创建JSON数组，JArrary
JArray arr = new JArray();arr.Add(new JValue(1));arr.Add(new JValue(2));arr.Add(new JValue(3));Console.WriteLine(arr.ToString());//返回//[// 1,// 2,// 3//]2、使用Linq创建JSON
使用LINQ声明式地创建JSON对象，是一种从值集合创建JSON的快速方法。
List posts = GetPosts();JObject rss = new JObject( new JProperty("channel", new JObject( new JProperty("title", "James Newton-King"), new JProperty("link", "http://james.newtonking.com"), new JProperty("description", "James Newton-King's blog."), new JProperty("item", new JArray( from p in posts orderby p.Title select new JObject( new JProperty("title", p.Title), new JProperty("description", p.Description), new JProperty("link", p.Link), new JProperty("category", new JArray( from c in p.Categories select new JValue(c)))))))));Console.WriteLine(rss.ToString());//{// "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 being available on CodePlex",// "link": "http://james.newtonking.com/projects/json-net.aspx",// "category": [// "Json.NET",// "CodePlex"// ]// },// {// "title": "LINQ to JSON beta",// "description": "Announcing LINQ to JSON",// "link": "http://james.newtonking.com/projects/json-net.aspx",// "category": [// "Json.NET",// "LINQ"// ]// }// ]// }//}3、从对象创建JSON
JObject.FromObject(object o)：o为要转化的对象，返回一个JObject对象
最后一个选项是使用FromObject()方法从非JSON类型创建JSON对象。
下面的示例展示了如何从匿名对象创建JSON对象，但是任何. net类型都可以与FromObject一起创建JSON。
var posts = new[] { new { Title="Json.NET 1.3 + New license + Now on CodePlex", Description= "Announcing the release of Json.NET 1.3, the MIT license and being available on CodePlex", Link="http://james.newtonking.com/projects/json-net.aspx", Categories=new[]{ "Json.NET","CodePlex"} }, new { Title="LINQ to JSON beta", Description= "Announcing LINQ to JSON", Link="http://james.newtonking.com/projects/json-net.aspx", Categories=new[]{ "Json.NET","LINQ"} },};JObject o = JObject.FromObject(new{ channel = new { title = "James Newton-King", link = "http://james.newtonking.com", description = "James Newton-King's blog.", item = //返回数组 from p in posts orderby p.Title select new { title = p.Title, description = p.Description, link = p.Link, category = p.Categories } }});Console.WriteLine(o.ToString());//{// "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 being available on CodePlex",// "link": "http://james.newtonking.com/projects/json-net.aspx",// "category": [// "Json.NET",// "CodePlex"// ]// },// {// "title": "LINQ to JSON beta",// "description": "Announcing LINQ to JSON",// "link": "http://james.newtonking.com/projects/json-net.aspx",// "category": [// "Json.NET",// "LINQ"// ]// }// ]// }//}4、解析JSON文本
JObject.Parse(string json)：json含有JSON对象的字符串，返回为JObject对象
//解析JSON对象string json = @"{ CPU: 'Intel', Drives: [ 'DVD read/writer', '500 gigabyte hard drive' ]}";JObject o = JObject.Parse(json);//解析JSON数组string json = @"[ 'Small', 'Medium', 'Large']";JArray a = JArray.Parse(json);5、从文件中加载JSON
using (StreamReader reader = File.OpenText(@"c:\person.json")){ JObject o = (JObject)JToken.ReadFrom(new JsonTextReader(reader)); // do stuff}二、使用JsonConvert.DeserializeObject反序列化JOSN片段
1、数组数据
string jsonArrayText= "[{'a','al'.'b','b1'},{'a','a2'.'b','b2'}]";JArray ja = (JArray)JsonConvert.DeserializeObject(jsonArrayText); string ja1a==ja[1]["a"].ToString(); //或者 JObject o=(JObject)ja[1]; string ja1a=o["a"].ToString();2、对象格式
siring jsonText= "{\"beijing\":{\"zone\":\"海淀\",\"zone_en\":\"haidian\"}";JObject jo =(JObject)JsonConvert.DeserializeObject(jsonArrayText);string zone =jo["beijing"]["zone"].ToString();三、修改JObject and JArrary实例
string json = @"{ 'post':{ 'Title':'修改JArray和JObject', 'Link':'http://write.blog.csdn.net', 'Description':'这是一个修改JArray和JObject的演示案例', 'Item':[] } }";JObject o = JObject.Parse(json);JObject post = (JObject)o["post"];post["Title"] = ((string)post["Title"]).ToUpper();post["Link"] = ((string)post["Link"]).ToUpper();post.Property("Description").Remove();post.Property("Link").AddAfterSelf(new JProperty("New", "新添加的属性"));JArray a = (JArray)post["Item"];a.Add("修改JArray");a.Add("修改JObject");移除属性
JObject jObj = JObject.Parse(json);jObj.Remove("Colleagues");//跟的是属性名称Console.WriteLine(jObj.ToString());四、查询JObject and JArrary实例
将一个值从LINQ转换为JSON的最简单方法是：使用JObject/JArray上的ItemObject索引，然后将返回的JValue转换为所需的类型。
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<string> categoriesText = categories.Select(c => (string)c).ToList();// Json.NET// CodePlex判断Key是否存在
JToken test = new JObject();if (test["a"] == null){ Console.WriteLine("键值key不存在！");}JObject test1 = test as JObject;if (test1.Property("a") == null || test1.Property("a").ToString() == ""){ Console.WriteLine("键值key不存在！");}五、用LINQ表达式进行查询
也可以使用LINQ查询JObject/JArray。
Children()以IEnumerable的形式返回JObject/JArray的子值，然后可以使用标准的Where/OrderBy/Select LINQ操作符查询这些子值。
注意：
Children()返回token的所有子元素。如果它是一个JObject，它将返回一个要使用的属性集合，如果它是一个JArray，您将得到一个数组值的集合。
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<string>() 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可以使用LINQ to JSON手动将JSON转换为. net对象。
当您处理与. net对象不匹配的JSON时，手动序列化和反序列化. net对象是很有用的。
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 takenpublic 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; }}六、使用函数SelectToken生成JToken对象可以简化查询语句
1、SelectToken
SelectToken是JToken上的一个方法，它将字符串路径作为子Token名，返回子Token。如果在路径的位置找不到Token，则SelectToken返回空引用。
该路径由属性名和按句点分隔的数组索引组成，例如manufacturer [0]. name。
JObject jObj = JObject.Parse(json);JToken name = jObj.SelectToken("Name");Console.WriteLine(name.ToString());结果：Jack
2、使用LINQ来SelectToken
SelectToken支持JSONPath查询。点击这里了解更多关于JSONPath的信息。
查询最后一名同事的年龄
//将json转换为JObjectJObject jObj = JObject.Parse(json);var age = jObj.SelectToken("Colleagues[1].Age");Console.WriteLine(age.ToString());// manufacturer with the name 'Acme Co'JToken acme = o.SelectToken("$.Manufacturers[?(@.Name == 'Acme Co')]");Console.WriteLine(acme);// { "Name": "Acme Co", Products: [{ "Name": "Anvil", "Price": 50 }] }// name of all products priced 50 and aboveIEnumerable pricyProducts = o.SelectTokens("$..Products[?(@.Price >= 50)].Name");foreach (JToken item in pricyProducts){ Console.WriteLine(item);}// Anvil// Elbow Grease结果：29
3、使用JSONPath来SelectToken
SelectToken可以与标准的LINQ方法结合使用。
利用SelectToken来查询所有同事的名字
JObject jObj = JObject.Parse(json);var names = jObj.SelectToken("Colleagues").Select(p => p["Name"]).ToList();foreach (var name in names) Console.WriteLine(name.ToString());IList<string> storeNames = o.SelectToken("Stores").Select(s => (string)s).ToList();// Lambton Quay// Willis StreetIList<string> firstProductNames = o["Manufacturers"].Select(m => (string)m.SelectToken("Products[1].Name")).ToList();// null// Headlight Fluiddecimal totalPrice = o["Manufacturers"].Sum(m => (decimal)m.SelectToken("Products[0].Price"));结果：Tom Abel
七、如果Json中的Key是变化的但是结构不变，如何获取所要的内容?
例如:
{ "trends": { "2013-05-31 14:31": [ { "name": "我不是谁的偶像", "query": "我不是谁的偶像", "amount": "65172", "delta": "1596" }, { "name": "世界无烟日", "query": "世界无烟日", "amount": "33548", "delta": "1105" } ] }, "as_of": 1369981898}其中的"2013-05-31 14:31"是变化的key，如何获取其中的"name","query","amount","delta"等信息呢?
通过Linq可以很简单地做到:
var jObj = JObject.Parse(jsonString);var tends = from c in jObj.First.First.First.First.Children() select JsonConvert.DeserializeObject(c.ToString());public class Trend{ public string Name { get; set; } public string Query { get; set; } public string Amount { get; set; } public string Delta { get; set; }}八、综合实例
void Main(){ string json = "{\"Name\" : \"Jack\", \"Age\" : 34, \"Colleagues\" : [{\"Name\" : \"Tom\" , \"Age\":44},{\"Name\" : \"Abel\",\"Age\":29}] }"; // 获取员工名称 JObject jObject = JObject.Parse(json); var name = jObject.Value<string>("Name"); Console.WriteLine(name); // 获取员工年龄 JToken jToken = jObject.SelectToken("Age"); Console.WriteLine(jToken.ToString()); // 获取同事信息 JToken jToken1 = jObject["Colleagues"]; Console.WriteLine(jToken1.ToString()); Console.WriteLine("============================="); // 获取员工同事的所有姓名 var names = from staff in jToken1.Children() select (string)staff["Name"]; // var names = jObject.SelectToken("Colleagues").Select(p => p["Name"]).ToList(); foreach (var item in names) { Console.WriteLine(item); } Console.WriteLine("============================="); // 修改Jack的年龄 jObject["Age"] = 99; Console.WriteLine(jObject.ToString()); // 修改同事Tome的年龄 jToken1[0]["Age"] = 45; Console.WriteLine(jObject.ToString()); Console.WriteLine("============================="); // Abel离职了 jObject["Colleagues"][1].Remove(); Console.WriteLine(jObject.ToString()); // 移除Jack的同事 jObject.Remove("Colleagues"); Console.WriteLine(jObject.ToString()); Console.WriteLine("============================="); // Jack缺少部门信息 jObject["Age"].Parent.AddAfterSelf(new JProperty("Department", "总裁办")); // 来了一个新员工Jerry JObject linda = new JObject(new JProperty("Name", "Linda"), new JProperty("Age", "23")); jObject.Add(new JProperty("Colleagues", new JArray() { linda })); Console.WriteLine(jObject.ToString());}// Define other methods and classes here以上就是“C#中的Linq to JSON操作实例分析”这篇文章的所有内容，感谢各位的阅读！相信大家阅读完这篇文章都有很大的收获，小编每天都会为大家更新不同的知识，如果还想学习更多的知识，请关注编程网行业资讯频道。
