​

public class ParentClass

{

    protected int Id;

    public ParentClass(int id)

    {

        this.Id = id;

    }

}

​

internal class ChieldClass : ParentClass

{

    private static int GetAppId()

    {

        //Здесь сложный рассчет id

        return 7;

    }

​

    private ChieldClass(int id) : base(id) { }

​

    public ChieldClass() : this(GetAppId()) { }

}