using System.IO;

using System.Text.Json;

using System.Threading.Tasks;

public class Program

{

    public static async Task Main()

    {

​

        var x = new { First = "Test", Second = 2 };

        System.Console.WriteLine(JsonSerializer.Serialize(x));

        await File.WriteAllTextAsync("data.json", JsonSerializer.Serialize(x)); 

    }

}