How to create a c# object and serialize it

Question

In C# I want to created JSON String or Object with the format below:

{
    "retailer_br_id" : "5473182",
    "retailer_external_id": "",
    "erp_invoice_number" : "INV-202302",
    "invoice_date": "2023-04-06T17:00:00.000Z",
    "status" : 1,
    "details":[{
        "sku_external_id": "TD5015151432201",
        "quantity" : "2",
        "price_per_item": "14.5"
        },
        {
            "sku_external_id": "000005020170898446",
            "quantity" : 1,
            "price_per_item": 10.50
        }
    ]
}

I tried the following, but it seems not working, it only gives me the dList value...................................................................................................................................

DataTable dt = new DataTable("Details");
dt.Columns.Add("sku_external_id", typeof(string));

//Data  
dt.Rows.Add("0000000000");
dt.Rows.Add("111111111");
dt.Rows.Add("1222222222");
dt.Rows.Add("3333333333");

Root rt = new Root();
rt.retailer_br_id = "32423432432424";
rt.retailer_external_id = "";
rt.erp_invoice_number = "PBY-202304";
DateTime d = DateTime.Now;
string dateString = d.ToString("Y-m-d H:i:s");
rt.invoice_date = dateString;

List<Detail> dList = new List<Detail>();

for (int i = 0; i < dt.Rows.Count; i++)
{
    Detail det = new Detail();
    
    det.sku_external_id = (string)dt.Rows[i]["sku_external_id"];
    
    dList.Add(det);
}

string json = JsonConvert.SerializeObject(dList, Formatting.Indented);
textBox1.Text = json;

Answer 1

1. You are serializing dList, but not root, this is why it show the serialized dList.

2. Missing assign the dList to rt.details.

rt.details = dList;
        
string json = JsonConvert.SerializeObject(rt, Formatting.Indented);

3. To serialize date to ISO 8601 format:

string dateString = d.ToString("yyyy-MM-ddTHH:MM:sss.fffZ");

Alternatives

1. Instead of using foreach loop to iterate and add items into dList, you may achieve with:

dList = JArray.FromObject(dt)
    .ToObject<List<Detail>>();

2. Name the properties as Pascal Case, and use JsonProperty attribute to define the property name used in serialization and deserialization.

public class Detail 
{ 
    [JsonProperty("sku_external_id")] 
    public string SkuExternalId { get; set; }

    [JsonProperty("quantity")]
    public object Quantity { get; set; }

    [JsonProperty("price_per_item")]
    public object PricePerItem { get; set; }
}

public class Root
{
    [JsonProperty("retailer_br_id")]
    public string RetailerBrId { get; set; }

    [JsonProperty("retailer_external_id")]
    public string RetailerExternalId { get; set; }

    [JsonProperty("erp_invoice_number")]
    public string ErpInvoiceNumber { get; set; }

    [JsonProperty("invoice_date")]
    public DateTime InvoiceDate { get; set; }

    [JsonProperty("status")]
    public int Status { get; set; }

    [JsonProperty("details")]
    public List<Detail> Details { get; set; }
}

3. Change invoice_date property to DateTime type so it will serialize and display the format in ISO 8601, instead of defining the format manually.

rt.invoice_date = DateTime.Now;

[JsonProperty("invoice_date")]
public DateTime invoice_date { get; set; }