C# 0 The Complete Reference

ArgumentException

 if the type of 

obj

 is not compatible for comparison with the 

invoking object.

Here is an example that shows how to implement 

IComparable

. It adds 

IComparable

to the 

Inventory

 class developed in the preceding section. It implements 

CompareTo( )

 so 

that it compares the 

name

 field, thus enabling the inventory to be sorted by name. By 

implementing

IComparable

, it allows a collection of 

Inventory

 objects to be sorted, as the 

program illustrates.

// Implement IComparable.

using System;

using System.Collections;

// Implement the non-generic IComparable interface.

class Inventory : IComparable {

  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);

  }

  // Implement the IComparable interface.

  public int CompareTo(object obj) {

    Inventory b;

    b = (Inventory) obj;

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