using System;

using System.Collections.Generic;

​

​

public class Data

{

    public int Id { get; set; }

}

​

public class InfoData<TInfo> : Data

    where TInfo: InfoBase

{

    public TInfo Info { get; set; }

}

​

/* Info classes */

​

public abstract class InfoBase

{

    public int Id { get; set; }

}

​

public interface IRelated

{

    IList<InfoBase> Related {get; set;}

}

​

public class ExtraInfo : InfoBase, IRelated

{

    public string Extras { get; set; }

    public IList<InfoBase> Related { get; set; }

}

​

public class OtherInfo : InfoBase, IRelated

{

    public DateTime Created { get; set; }

    public IList<InfoBase> Related { get; set; }

}

​

​

public class Program

{

    public static void Show<TData>(string descriptor, int id, int? related = null)

        where TData: Data

    {

        Console.WriteLine("{0}: id={1} related={2}", descriptor, id, related);

    }

​

    public static TData Add<TData>(TData data)

        where TData: Data

    {

        Show<TData>("Add<TData>", data.Id);

        return data;

    }

​

    public static TData Add<TData, TInfo>(TData data)

        where TData: InfoData<TInfo>

        where TInfo: InfoBase, IRelated

    {

        Show<TData>("Add<TData,TInfo>", data.Id, data.Info.Related[0].Id);

        return data;

    }

​

    public static void Main(string[] args) {

        Add(new Data {

            Id = 1

        });

        Add(new InfoData<ExtraInfo> {

            Id = 2,

            Info = new ExtraInfo {

                Id = 10,

                Extras = "Extra Info",

                Related = new List<InfoBase> {

                    new OtherInfo {

                        Id = 20

                    }

                }

            }

        });

        Add<InfoData<ExtraInfo>, ExtraInfo>(new InfoData<ExtraInfo> {

            Id = 2,

            Info = new ExtraInfo {

                Id = 10,

                Extras = "Extra Info",

                Related = new List<InfoBase> {

                    new OtherInfo {

                        Id = 20

                    }

                }

            }

        });

        Add<InfoData<OtherInfo>, OtherInfo>(new InfoData<OtherInfo> {

            Id = 2,

            Info = new OtherInfo {

                Id = 10,

                Created = DateTime.Now,

                Related = new List<InfoBase> {

                    new ExtraInfo {

                        Id = 10

                    }

                }

            }

        });

    }

}