using System;

using System.Collections.Generic;

using System.Text.Json;

​

public class Program

{

    public abstract class Detail

    {

        /// <summary>

        /// Field to indicate when the activity happened in UTC

        /// </summary>

        public DateTime ActivityDateTimeUtc { get; init; }

        /// <summary>

        /// Field to indicate Lead Response Time adjusted based on Dealer hours

        /// </summary>

        public decimal ResponseTimeAdjusted { get; init; }

        public abstract DateTime SoldDate { get; init; }

    }

​

    public class PendingSalesDetail : Detail

    {

        public override DateTime SoldDate { get; init; }

    }

​

    public class OpenVisitsDetail : Detail

    {

        public override DateTime SoldDate { get; init; }

        public DateTime VisitDate { get; init; }

    }

​

    public static void Main()

    {

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

        details.Add(new PendingSalesDetail() { SoldDate = DateTime.Now });

        details.Add(new OpenVisitsDetail() { VisitDate = DateTime.Now });

        string jsonString = JsonSerializer.Serialize(details);

        Console.WriteLine(jsonString);

    }

}