Setup Code

private static IDictionary<string, object> testAttributes = new Dictionary<string, object>()
    {
        { "House", 1 },
        { "Street", "Musterstraße" },
        { "Single", true }
    };

    private static List<Person> data = new List<Person>()
    {
        new Person() { ID = 1, Name = "Max", Surname = "Mustermann", AdditionalData = testAttributes },
        new Person() { ID = 2, Name = "Resa", Surname = "Rito", AdditionalData = testAttributes }
    };

    public List<Person> Persons { get; set; } = data;
    public Person TestType { get; set; } = new Person();

 public class Person
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public string Surname { get; set; }
        public Dictionary<string, object> AdditionalData { get; set; } = new Dictionary<string, object>();
    }