c# 从json中获取值

Question

我有一个 json 文本，我想获取作者姓名和描述标签的值。不需要其他字段，例如 url 和 urltoimage 等等。 当我运行以下代码时，不提供任何字符串值。我认为这里有一些错误。

{
  "status": "ok",
  "articles": [
  {
    "source": {
      "id": "techcrunch",
      "name": "TechCrunch"
    },
    "author": "Khaled \"Tito\" Hamze",
    "title": "Crunch Report",
    "description": "Your daily roundup of the biggest TechCrunch stories and startup news.",
    "url": "https://techcrunch.com/video/crunchreport/",
    "urlToImage": "https://tctechcrunch2011.files.wordpress.com/2015/03/tccrshowogo.jpg?w=500&h=200&crop=1",
    "publishedAt": "2017-12-11T20:20:09Z"
  },
  {
    "source": {
      "id": "techcrunch",
      "name": "TechCrunch"
    },
    "author": "Sarah Perez",
    "title": "Facebook is trying to make the Poke happen again",
    "description": "Facebook's \"Poke\" feature has never really gone away, but now the social network is giving it a more prominent placement - and is even considering expanding..",
    "url": "https://techcrunch.com/2017/12/11/facebook-is-trying-to-make-the-poke-happen-again/",
    "urlToImage": "https://tctechcrunch2011.files.wordpress.com/2017/12/facebook-poke-icon.jpg",
    "publishedAt": "2017-12-11T20:02:30Z"
  },
  {
    "source": {
      "id": "techcrunch",
      "name": "TechCrunch"
    },
    "author": "Sarah Perez",
    "title": "Amazon Alexa can now wake you up to music",
    "description": "This fall, Amazon made a play to become your new alarm clock with the introduction of a combination smart speaker and clock called the Echo Spot. Today, the..",
    "url": "https://techcrunch.com/2017/12/11/amazon-alexa-can-now-wake-you-up-to-music/",
    "urlToImage": "https://tctechcrunch2011.files.wordpress.com/2017/09/amazon-event-9270069.jpg",
    "publishedAt": "2017-12-11T17:22:30Z"
  },
  {
    "source": {
      "id": "techcrunch",
      "name": "TechCrunch"
    },
    "author": "Ingrid Lunden, Katie Roof",
    "title": "Apple confirms Shazam acquisition; Snap and Spotify also expressed interest",
    "description": "After we broke the story last week that Apple was acquiring London-based music and image recognition service Shazam, Apple confirmed the news today. It is..",
    "url": "https://techcrunch.com/2017/12/11/apple-shazam-deal/",
    "urlToImage": "https://tctechcrunch2011.files.wordpress.com/2017/12/shazam-app-icon-ios.jpg",
    "publishedAt": "2017-12-11T15:59:31Z"
  }
]}

如何获得这个？下面是我的代码，它根本不起作用

var data = (JObject)JsonConvert.DeserializeObject(myJSON);
string nameArticles= data["articles"].Value<string>();
MessageBox.Show(nameArticles);


   public class Source
   {
    public string id { get; set; }
    public string name { get; set; }
   }
   public class Article
   {
    public Source source { get; set; }
    public string author { get; set; }
    public string title { get; set; }
    public string description { get; set; }
    public string url { get; set; }
    public string urlToImage { get; set; }
    public DateTime publishedAt { get; set; }
   }

            Article art = new Article();

            art = JsonConvert.DeserializeObject<Article>(myJSON);

            MessageBox.Show(art.description.ToString());

以上代码返回对象未设置为实例错误！

Answer 1

data["articles"] 可能是 JArray 而不是字符串。您需要遍历前面提到的JArray 中的每个JObject，提取作者和描述值

var data = (JObject)JsonConvert.DeserializeObject(myJSON);
var articles = data["articles"].Children();

foreach (var article in articles)
{
    var author = article["author"].Value<string>();
    var description = article["author"].Value<string>();

    Console.WriteLine($"Author: " + author + ", Description: " + description);
}

这应该可以帮助您开始您正在做的任何事情。

Answer 2

如果不想创建包装类，可以试试下面的代码 sn-p，它使用了dynamic type 到deserialize JSON into an object。

var json = "Your JSON string";

dynamic stuff = JsonConvert.DeserializeObject(json);

string name = stuff.status;
var arr = stuff.articles;

foreach (var a in arr)
{
   var authorName = a.author;
}

Answer 3

假设您希望反序列化为具体类（根据您的问题中显示的第二种尝试方法），那么您需要一个包装类来保存整个对象，并对其进行反序列化。

目前您正尝试将整个对象序列化为 Article，但只有该对象的 articles 数组中的单个对象才能匹配您的 Article 类中的结构。

您试图在对象的错误级别执行操作，而且您忘记了 articles 是一个列表（数组）这一事实。

类似这样的：

public class JSONResponse
{
    public string status { get; set; }
    public List<Article> articles { get; set; }
}

和

JSONResponse response = JsonConvert.DeserializeObject<JSONResponse>(myJSON);

然后您可以使用普通循环遍历response.articles 列表并提取作者姓名和描述。

Answer 4

您的 Json 制作下面的一组类

public class Source
{ 
  public string id { get; set; } 
  public string name{get;set;}
}
public class Article
{
public Source source { get; set; }
public string author { get; set; }
public string title { get; set; }
public string description { get; set; }
public string url { get; set; }
public string urlToImage { get; set; }
public DateTime publishedAt { get; set; }
}

public class RootObject
{
public string status { get; set; }
public List<Article> articles { get; set; }
}

所以你通过以下方式反序列化这个..

var data = JsonConvert.DeserializeObject<RootObject>(myJSON);
nameArticles=data.articles.FirstOrDefault().description;
MessageBox.Show(nameArticles);

Answer 5

示例 json 数据

string jsonString = "{\"displayName\":\"Alex Wu\",\"signInNames\":[{\"type\":\"emailAddress\",\"value\":\"AlexW@example.com\"},{\"type\":\"emailAddress\",\"value\":\"AlexW2@example.com\"}]}";

将 json 转换为 jObject 并使用名为 selectToken() 的内置方法获取值

JObject jObject = JObject.Parse(jsonString);
        string displayName = (string)jObject.SelectToken("displayName");
        string type = (string)jObject.SelectToken("signInNames[0].type");
        string value = (string)jObject.SelectToken("signInNames[0].value");
        Console.WriteLine("{0}, {1}, {2}", displayName, type, value);
        JArray signInNames = (JArray)jObject.SelectToken("signInNames");
        foreach (JToken signInName in signInNames)
        {
            type = (string)signInName.SelectToken("type");
            value = (string)signInName.SelectToken("value");
            Console.WriteLine("{0}, {1}",  type, value);
        }

谢谢

Answer 6

请为您的 JSON 文件创建一个类并为所有标签添加属性 然后编写如下代码：

public class exampleJson{
public string author {get;set;}
public string description {get;set;}
.....

}

var data = JsonConvert.DeserializeObject<exampleJson>(myJSON);
string authorName = data.author;
string descriptions = data.description ;

Answer 7

使用Json.NET

示例：

        String[] your_json_file = Directory.GetFiles("C:\your_folder", json_file_name.json", SearchOption.AllDirectories);
        foreach (string s in your_json_file)
        {
            JObject JSON = JObject.Parse(File.ReadAllText(s));
            string AutorName = (string)JSON["author"];
            string Description = (string)JSON["description"];
        }