Saving data in json format using c#

Question

I want to save data in local json file in this format:

[
{"Name":"sdafdsf","Password":"dsfads","FirstName":"fsdf","LastName":"dsfdafas"},
{"Name":"sddafdsf","Password":"dsfadds","FirstName":"fdsdf","LastName":"dsfdafasdfs"} 
]

I am using this in the controller to serialize into json format:

 public ActionResult Index(demo obj)
        {

            String json = Newtonsoft.Json.JsonConvert.SerializeObject(obj);
            string path = Server.MapPath("~/app/");
            //// Write that JSON to txt file,  
            //var read = System.IO.File.ReadAllText(path + "output.json");
            System.IO.File.WriteAllText(path + "output.json",  json);
            return View();
        }

This is my model:

public class demo
    {

        public string Name { get; set; }
        public string Password { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }

But instead of proper JSON format I am getting this in my output.json file:

{"Name":"sdafdsf","Password":"dsfads","FirstName":"fsdf","LastName":"dsfdafas"}{"Name":"adfsdsfsafdsafasdfsdfsadf","Password":"dfsaasdsa","FirstName":"safd","LastName":"dfsafads"}

How can I save data in the proper format?

Answer 1

This is the proper format, if you mean you need it like an array then add the object to an array and after that serialize it:

 public ActionResult Index(demo obj)
        {
    var array = new [] {obj};
            String json = Newtonsoft.Json.JsonConvert.SerializeObject(array);
            string path = Server.MapPath("~/app/");
            //// Write that JSON to txt file,  
            //var read = System.IO.File.ReadAllText(path + "output.json");
            System.IO.File.WriteAllText(path + "output.json",  json);
            return View();
        }  

Or:

var list = new List<demo>();
list.Add(obj);
String json = Newtonsoft.Json.JsonConvert.SerializeObject(list);

if you want to keep data always in an array then you always need to:

1. read data from the json file.
2. deserialize as a list of `List'.
3. add the new item to this list.
4. serialize it again and save it over that file replacing all the old text with the new one.

like this:

 public ActionResult Index(demo obj)
        {
          string path = Server.MapPath("~/app/");
        var read = System.IO.File.ReadAllText(path + "output.json");
        List<demo> lst = Newtonsoft.Json.JsonConvert.DeserializeObject<List<demo>>(read);
        if (lst == null)
        {
            List<demo> _data = new List<demo>();
            _data.Add(obj);
           String json = Newtonsoft.Json.JsonConvert.SerializeObject(_data.ToArray());
            System.IO.File.WriteAllText(path + "output.json", json);
        }
        else
        {
            lst.Add(obj);
            String json = Newtonsoft.Json.JsonConvert.SerializeObject(lst);
            System.IO.File.WriteAllText(path + "output.json", json);
        }
        return View();
        }  

Of course you can write cleaner code by separate some pieces.