How to deserialize multiple JSON objects in C#?

Question

I'm passing multiple JSON objects from my frontend to a C# backend - how can I deserialize them into C# classes so they can be used later on in my application? Before I go any farther, I am tied to using the JS FormData object, contentType: false, and processData: false, because I also need to pass files via this AJAX call; that is completely unrelated to this question. Here's my code so far:

Frontend - function is called when a submit button is pressed

submitData: function () {
    var formCollection = this.appModel.get('formCollection').models;
    var formData = new FormData();
    var formJson = [];
    $.each(formCollection, function (index, form) {
        var tempJson = {};
        if (form) {
            tempJson['id'] = form.get('id');
            tempJson['number'] = form.get('number');
            tempJson['name'] = form.get('name');
            tempJson['attachments'] = form.get('attachments');
            formJson.push(tempJson);
        }
    });
    console.log(JSON.stringify(formJson));
    formData.append('formJson', JSON.stringify(formJson));
    $.ajax({
        type: "POST",
        url: '/NMISProduct/Test',
        contentType: false,
        processData: false,
        data: formData,
        success: function (result) {
            console.log(result);
        }
    });
}

JSON.stringified data that's being passed

[{"id":1,"number":null,"name":"Investment Portfolio Statement","attachments":null},{"id":2,"number":"61-0227","name":"WMC Signature Portfolio Agreement","attachments":null},{"id":3,"number":"61-1126","name":"WMC Signature Choice Agreement","attachments":null},{"id":4,"number":"61-1162","name":"WMC Signature Annuities Agreement","attachments":null},{"id":5,"number":"61-1205","name":"WMC Signature Managed Accounts Client Agreement","attachments":null}]

C# MVC 5 Backend

[HttpPost]
public async Task<JsonResult> Test()
{
    Debug.WriteLine(Request.Params["formJson"]);
    var forms = JsonConvert.DeserializeObject<Form>(Request.Params["formJson"]);
    Debug.WriteLine(forms);
    try
    {
        var srNumber = GetSRNumber();
        foreach (string file in Request.Files)
        {
            var fileContent = Request.Files[file];
            Debug.WriteLine(ReadFileInputStream(fileContent));
            if (fileContent != null && fileContent.ContentLength > 0)
            {
                // get a stream
                var stream = fileContent.InputStream;
                // and optionally write the file to disk
                //var fileName = Path.GetFileName(file);
                var fileName = fileContent.FileName;
                var path = Path.Combine(Server.MapPath("~/App_Data/"), fileName);
                using (var fileStream = System.IO.File.Create(path))
                {
                    stream.CopyTo(fileStream);
                }
            }
        }
    }
    catch (Exception)
    {
        return Json("Upload failed");
    }
    return Json("File uploaded successfully");
}

public class Form
{
    public int id { get; set; }
    public string number { get; set; }
    public string name { get; set; }
    public Form attachments { get; set; }
    public byte[] fileAsBytes { get; set; }
}

I've done my research and found several Stackoverflow questions that show how to serialize one JSON object into one C# class - however, I need to serialize multiple JSON objects into a List<Form>. How can I do this? What am I doing wrong in the posted code?

Answer 1

You're trying to deserialize to a single form here:

var forms = JsonConvert.DeserializeObject<Form>(Request.Params["formJson"]);

Just change it to:

var forms = JsonConvert.DeserializeObject<List<Form>>(Request.Params["formJson"]);

You should then be able to use forms in a normal way - iterating over it, taking a count etc.