Implements IComparable

   
 


using System;
using System.Collections.Generic;

public class Book : IComparable<Book> {
    private string name;
    private int circulation;

    private class AscendingCirculationComparer : IComparer<Book> {
        public int Compare(Book x, Book y) {
            if (x == null &amp;&amp; y == null) return 0;
            else if (x == null) return -1;
            else if (y == null) return 1;
            if (x == y) return 0;
            return x.circulation - y.circulation;
        }
    }
    public Book(string name, int circulation) {
        this.name = name;
        this.circulation = circulation;
    }

    public static IComparer<Book> CirculationSorter {
        get { return new AscendingCirculationComparer(); }
    }

    public override string ToString() {
        return string.Format("{0}: Circulation = {1}", name, circulation);
    }

    public int CompareTo(Book other) {
        if (other == null) return 1;

        if (other == this) return 0;
        return string.Compare(this.name, other.name, true);
    }
}

public class MainClass {
    public static void Main() {
        List<Book> Books = new List<Book>();

        Books.Add(new Book("E", 1));
        Books.Add(new Book("T", 5));
        Books.Add(new Book("G", 2));
        Books.Add(new Book("S", 8));
        Books.Add(new Book("H", 5));

        foreach (Book n in Books) {
            Console.WriteLine("  " + n);
        }

        Books.Sort();
        foreach (Book n in Books) {
            Console.WriteLine("  " + n);
        }

        Books.Sort(Book.CirculationSorter);
        foreach (Book n in Books) {
            Console.WriteLine("  " + n);
        }
    }
}