Json.NET parse array in object

Question

I'm having an extremely difficult time parsing multiple arrays out of an array, embedded in several object in JSON.

Basically the json looks like

{
 took:8,
 success:true,
 items:[
  keywords:{...},
  mainInfo:{
    name:'...',
    expDate:'...',
    targetCities:[...],
    targetStates:[...]
  },
  additionalInfo:{
    skills:[],
    homeTime:''
  }
}

My C# looks like:

public class Job{
  public string name{get;set;}
  public List<string> targetCities{get;set;}
  public List<string> targetStates{get;set;}
  public List<string> skills{get;set;}
  public string homeTime{get;set;}
}
public class Jobs{
  private JObject o;
  private List<Job> jobs;
  public Jobs(string json){
    this.o=JObject.Parse(json);
  }
  public List<Job> toList(){
    List<JObject> allJobs=o["items"].Select(t => (JObject)t).ToList();
    foreach(JObject i in allJobs){
      Job j=new Job();
      j.name=(string)i["mainInfo"]["name"];
      j.targetCities=i["mainInfo"]["targetCities"].Select(t =>(string)t).ToList();
      j.targetStates=i["mainInfo"]["targetStates"].Select(t =>(string)t).ToList();
      j.expDate=(string)i["mainInfo"]["expDate"]
      j.skills=i["additionalInfo"]["skills"].Select(t =>(string)t).ToList();
      j.homeTime=(string)i["additionalInfo"]["homeTime"];
      this.jobs.Add(j); //ERROR
    }
    return this.jobs;
}

The error is a Null Reference Exception, with the info Object reference not set to an instance of an object., however it seems that this error jumps around almost unpredictably as I try and change my code to fix the bug.

I am by no means a C# or .NET expert. I had dealt with the language in the past, but I personally do not like it. So forgive me for any stupid error I may have made.

ADDITION:

I'm basically stepping through all the items and trying to create a Job object from each item using the data accordingly.

How is JObject defined?

Mihai Hantea
– Mihai Hantea

2014-03-10 00:40:04 +00:00
Commented Mar 10, 2014 at 0:40 — Mihai Hantea
– Mihai Hantea, Commented Mar 10, 2014 at 0:40
It's a JSON.net object

tsturzl
– tsturzl

2014-03-10 00:48:48 +00:00
Commented Mar 10, 2014 at 0:48 — tsturzl
– tsturzl, Commented Mar 10, 2014 at 0:48

Mihai Hantea · Accepted Answer · 2014-03-10 01:35:09Z

4

You forgot to initialize your jobs field, private List<Job> jobs; You don't need this private field if you alway generate the jobs list. Use a local variable.

public List<Job> toList()
        {
            jobs = new List<Job>(); //add this line
            List<JObject> allJobs = o["items"].Select(t => (JObject)t).ToList();
            foreach (JObject i in allJobs)
            {
                Job j = new Job();
                j.name = (string)i["mainInfo"]["name"];
                j.targetCities = i["mainInfo"]["targetCities"].Select(t => (string)t).ToList();
                j.targetStates = i["mainInfo"]["targetStates"].Select(t => (string)t).ToList();
                j.expDate = (string)i["mainInfo"]["expDate"];
                j.skills = i["additionalInfo"]["skills"].Select(t => (string)t).ToList();
                j.homeTime = (string)i["additionalInfo"]["homeTime"];
                this.jobs.Add(j); 
            }
            return this.jobs;
        }

edited Mar 10, 2014 at 1:35

answered Mar 10, 2014 at 1:29

Mihai Hantea

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3 Comments

tsturzl Over a year ago

I actually noticed this a bit ago. I also pulled jobs into the scope of the toList method rather than having it as a property. The problem actually happened to be that the developer who wrote the API spelled a bunch of keys wrong in the JSON while in the API documentation they are spelled correctly.

Mihai Hantea Over a year ago

Also the json was missing some brackets, I wanted to test and could not parse it. Anyway the error was coming from that variable.

tsturzl Over a year ago

the json provided was just simple mock-up. The json that I was dealing with was about 50x larger than the example.

user1108948 · Accepted Answer · 2014-03-10 00:27:50Z

1

I think that you may define allJobs first

List<JObject> allJobs = new List<JObject>();
allJobs=o["items"].Select(t => (JObject)t).ToList();

answered Mar 10, 2014 at 0:27

user1108948

4 Comments

tsturzl Over a year ago

.ToList() creates and assigns a List object.

user1108948 Over a year ago

Have you tried my code? If you don't define the instance, there is no memory allocated.

tsturzl Over a year ago

The instance is defined by the ToList method, however.

tsturzl Over a year ago

My jobs object, however, was never initialized. I'll give you +1 for bringing the thought to the table.

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