C# 0 The Complete Reference

PART II

C h a p t e r   2 4 :  

C o l l e c t i o n s ,   E n u m e r a t o r s ,   a n d   I t e r a t o r s    

807

This method compares 

obj1

 with 

obj2

 and returns greater than zero if 

obj1

 is greater than 

obj2,

 zero if the two objects are the same, and less than zero if 

obj1

 is less that 

obj2

.

Here is a generic version of the preceding program that uses 

IComparer

. It 

produces the same output as the previous versions of the program.

// Use IComparer.

using System;

using System.Collections.Generic;

// Create an IComparer for Inventory objects.

class CompInv : IComparer where T : Inventory {

  // Implement the IComparer interface.

  public int Compare(T obj1, T obj2) {

    return obj1.name.CompareTo(obj2.name);

  }

}

class Inventory {

  public string name;

  double cost;

  int onhand;

  public Inventory(string n, double c, int h) {

    name = n;

    cost = c;

    onhand = h;

  }

  public override string ToString() {

    return

      String.Format("{0,-10}Cost: {1,6:C}  On hand: {2}",

                    name, cost, onhand);

  }

}

class GenericIComparerDemo {

  static void Main() {

    CompInv comp = new CompInv();

    List inv = new List();

    // Add elements to the list.

    inv.Add(new Inventory("Pliers", 5.95, 3));

    inv.Add(new Inventory("Wrenches", 8.29, 2));

    inv.Add(new Inventory("Hammers", 3.50, 4));

    inv.Add(new Inventory("Drills", 19.88, 8));

    Console.WriteLine("Inventory list before sorting:");

    foreach(Inventory i in inv) {

      Console.WriteLine("   " + i);

    }

    Console.WriteLine();

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808

 

P a r t   I I :  

E x p l o r i n g   t h e   C #   L i b r a r y

    // Sort the list using an IComparer.

    inv.Sort(comp);

    Console.WriteLine("Inventory list after sorting:");

    foreach(Inventory i in inv) {

      Console.WriteLine("   " + i);

    }

  }

}