using System;

using System.Collections.Generic;

using Newtonsoft.Json;

public class Program

{

    public static void Main()

    {       

        var msg = new message() { Content = new content() { type = "text/html", value = "html" },

        From = new from() { email = "example@example.com", name = "example" },

        Personalizations = new personalizations() {subject="", tos = new List<to>() { new to(), new to() } } };

        var data = JsonConvert.SerializeObject(msg);

        Console.WriteLine(data);

    }

    class message

    {

        public content Content { get; set; }

        public from From { get; set;  }

        public personalizations Personalizations { get; set; }

    }

​

​

    public class content

    {

        public string type = "text/html";

        public string value = "html";

    }

​

    public class from

    {

        public string email = "example@example.com";

        public string name = "example";

​

    }

    public class personalizations

    {       

        public string subject { get; set; }

        public List<to> tos { get; set; }

    }

    public class to

    {

        public string email { get; set; }

    }

​

}