Example.csx

#r "nuget:Newtonsoft.Json, 13.0.1"

using Newtonsoft.Json;

public class Product
{
    public string Name { get; set; }
    public DateTime Expiry { get; set; }
    public string[] Sizes { get; set; }
}

Product product = new Product
    {
        Name = "Apple",
        Expiry = new DateTime(2008, 12, 28),
        Sizes = new string[] { "Small" },
    };

var json = JsonConvert.SerializeObject(product);
Console.WriteLine(json);