Question

I’m trying to properly write code to build a data structure to serialize into json.

I’m using json.net.

I don’t want to create a bunch of classes to hold this data, as I thought there should be some classes that will already do this in json.net

I’ve already got all the data I need in a series of nested loops, and now I just want to add them to an object hierarchy before I run JsonConvert.SerializeObject on it.

I’ve already tried code like this, but it doesn’t seem to work

JArray container = new JArray();

        container.Add(new JObject(new JProperty("name", "Client1"), new JProperty("projects", new JArray())));

        container[0].AddAfterSelf(new JObject(new JProperty("projects", new JArray())));            
        container[1].AddAfterSelf(new JObject(new JProperty("projects", "Project2")));
        container[1].AddAfterSelf(new JObject(new JProperty("projects", "Project3")));
        container.Add(new JProperty("name", "Client2"));            

        var test = JsonConvert.SerializeObject(container);

The problem is that when I use [i]. or ElementAt(i) to access somewhere in the structure, either .Add() is missing or .ElementAt isn’t there.
How do I step through the data structure to make this nicely output the below, or do I have to create my own container class for all of this?

This is the data format I am trying to make.

[
    {
    "name": "student1",
    "projects": 
    [
        {
        "name": "Project1",
        "tasks": 
                [
                    {
                    "name": "task1",
                    "id": 2
                    }
                ],
        "id": 6
        }
    ]
},
    {
    "name": "Student2",
    "projects": [
                {
                "name": "Project1",
                "tasks": [
                         {
                         "name": "Task2",
                         "id": 1
                         },
                         {
                         "name": "Task3",
                         "id": 3
                         },
                         {
                         "name": "Task4",
                         "id": 4
                         }
                         ],
                "id": 2

etc…

Answer 1

I think what you’re asking is how to serialize complex business objects in json, but only expose certain properties.

In other words you already have a list of students, but you only want to send very specific data via json. If I’m wrong this answer won’t suit your needs.

So assuming you have a list of students, with a projects property that has an inner property of tasks, this is how I do it without having to create loads of new classes, I use anonymous objects.

Once I’ve created my list of anonymous objects, I simply turn them into a json string.

As pointed out in the comments you don’t need to use json.net, this functionality is available in the framework, add a reference to System.Web.Extensions.dll then

using System.Web.Script.Serialization;

var jsonStudents = new List<object>();

foreach (var student in students)
{
    jsonStudents.Add(new
    {
        student.Id,         //anonymous properties automatically pick up the name of the property you pass them, this will be called Id
        FullName = student.FirstName + " " + student.LastName, //if you want to name a property yourself use this notation
        Projects = student.Projects.Select(p => new //this will be an enumerable of nested anonymous objects, we're partially selecting project properties
        {
            p.Id,
            p.Name,
            Tasks = p.Tasks.Select(t => new //nesting another level
            {
                t.Id,
                t.Name
            })
        })
    });
}

var serializer = new JavaScriptSerializer();

var jsonString = serializer.Serialize(jsonStudents);

If you really want to use loops you can do this to allow you to do more complicated things in the creating of the projects and tasks:

var jsonStudents = new List<object>();

foreach (var student in students)
{
    var tempStudent = new
    {
        student.Id,         //anonymous properties automatically pick up the name of the property you pass them, this will be called Id
        FullName = student.FirstName + " " + student.LastName, //if you want to name a property yourself use this notation
        Projects = new List<object>()
    };

    foreach (var project in student.Projects)
    {
        var tempProject = new {
            project.Id,
            project.Name,
            Tasks = new List<object>()
        };

        foreach (var task in project.Tasks)
        {
            tempProject.Tasks.Add(new {
                task.Id,
                task.Name
            });
        }

        tempStudent.Projects.Add(tempProject);
    }

    jsonStudents.Add(tempStudent);
}

var serializer = new JavaScriptSerializer();

var jsonString = serializer.Serialize(jsonStudents);