c# get values from json

问题

I have a json text and i want to get the values of author name and description tags. no need of other fields like url and urltoimage and all. when i run the below code does not providing any string values. i think some error goes here.

{
  "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"
  }
]}

how to get this? below is my code and its not at all working

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());

the above code return object not set to an instance error!

回答1:

Assuming you wish to deserialize to concrete classes (as per the second attempted approach shown in your question) then you need a wrapper class to hold the whole object, and deserialise to that. At the moment you're trying to serialise your entire object into a an Article, but only the individual objects within the "articles" array of that object would match the structure in your Article class. You're trying to do the action at the wrong level of your object, and also you're forgetting the fact that articles is a list (array).

Something like this:

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

and

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

Then you can use a normal loop to iterate through the response.articles list and extract the author names and descriptions.

回答2:

data["articles"] is likely to be a JArray not a string. You'll need to iterate over each JObject in the aforementioned JArray pulling out the author and description values

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);
}

This should help you get started with whatever you're doing.

回答3:

If you do not want to create a wrapper class, you can try the below code snippet, which uses the dynamic type to 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;
}

回答4:

Your Json make below set of class

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; }
}

So You Deserialize this by following way..

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

回答5:

Use Json.NET

Example:

        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"];
        }

回答6:

Please create a class for your JSON file and add property for all tags and then write code as below:

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 ;

来源：https://stackoverflow.com/questions/47772007/c-sharp-get-values-from-json

标签

json

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