using System;

using System.Collections.Generic;

using System.Text;

public class Program

{

    public static void Main()

    {

        var d = DateTime.Now;

        var article = new Article

        {

            Id = 1, 

            Date = d, 

            User = new AppUser 

            {

                Id = 1,

                Name = "Hello World!", 

                Things = new List<string> 

                { 

                    "Foo", 

                    "Bar"

                }

            },

            Deleted = true };

        Console.WriteLine(article.ToString());

    }

}

public class Article

{

    public int Id { get; set; }

    public AppUser User { get; set; }

    public DateTime Date { get; set; }

    public bool Deleted { get; set; }

    public override string ToString()

    {

        var sb = new StringBuilder();

        foreach (var property in typeof(Article).GetProperties())

        {

            if (property.PropertyType.Name == nameof(DateTime))

            {

                var d = DateTime.Parse(property.GetValue(this, null).ToString());

                sb.AppendLine($"{property.Name}: {d.ToString("dd/MM/yyyy")}");

            }

            else if (property.PropertyType.ToString() == nameof(AppUser))

            {

                foreach (var prop in property.PropertyType.GetProperties())

                {

                    if (prop.Name == "Name")

                        sb.AppendLine($"{prop.Name}: {prop.GetValue(User, null).ToString()}");

                    if (prop.Name == "Things")

                    {

                        var list = (List<string>)prop.GetValue(User, null);

                        foreach (var item in list)

                            sb.AppendLine($"  {item}");

                    }

                }

            }

            else

            {

                sb.AppendLine($"{property.Name}: {property.GetValue(this, null).ToString()}");

            }

        }

        return sb.ToString();

    }

}

​

public class AppUser

{

    public int Id { get; set; }

    public string Name { get; set; }

    public List<string> Things { get; set; }

}