using System;

public class Program

{

    public static void Main()

    {

        var x = new Subject();

        x.Id = 5;

        Console.WriteLine("Hello World");

    }

}

​

public class Core<T> {

​

    public virtual T Id { get; set; }   

}

​

public class Core {

}

​

public class CoreWithId : Core<int> {

}

​

public class Subject : CoreWithId {

}