public class Class

{

    public string Letter { get; set; }

    public int Number { get; set; }

    public Class (int number, string letter) { this.Letter = letter; this.Number = number; }

}

public class Student

{

    public string Name { get; set; }

    public Class Class { get; set; }

    public int NumberInClass { get; set; }

    public string UniqueClassNumber

    {

        get

        {

            return this.Class.Number + this.Class.Letter + this.NumberInClass

        }

    }

    public Student (string name, int number, Class class) { ... }

}



И съответно

Class c = new Class(11, "a");

Student pesho = new Student("pesho", 16, c);

Console.WriteLine(pesho.UniqueNumber); // 11a16