C# 0 The Complete Reference

IList

, is implemented by 

List

, as shown here:

public T this[int 

idx

] { get; set; }

It sets or gets the value of the element at the index specified by 

idx.

Here is a program the demonstrates 

List

. It reworks the first 

ArrayList

 program 

shown earlier in this chapter. The only changes necessary are to substitute the name 

List

 for 

ArrayList

 and to use the generic type parameters.

// Demonstrate List.

using System;

using System.Collections.Generic;

class GenListDemo {

  static void Main() {

    // Create a list.

    List lst = new List();

    Console.WriteLine("Initial number of elements: " +

                       lst.Count);

    Console.WriteLine();

    Console.WriteLine("Adding 6 elements");

    // Add elements to the list.

    lst.Add('C');

    lst.Add('A');

public void

    Sor t(int 

star tIdx

, int 

count

,

           IComparer 

comp

)

Sor ts a por tion of the collection using the specified 

comparison object. The sor t begins at 

star tIdx

 and 

runs for 

count

 elements

.

 If 

comp

 is null, the default 

comparer for each object is used.

public T[ ] ToArray( )

Returns an array that contains copies of the elements 

of the invoking object.

public void TrimExcess( )

Reduces the capacity of the invoking list so that it is 

no more than 10 percent greater than the number of 

elements that it currently holds.

T

ABLE

 24-14 

A Sampling of Methods Defi ned by 

List

(continued)

Method

Description

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    lst.Add('E');

    lst.Add('B');

    lst.Add('D');

    lst.Add('F');

    Console.WriteLine("Number of elements: " +

                       lst.Count);

    // Display the list using array indexing.

    Console.Write("Current contents: ");

    for(int i=0; i < lst.Count; i++)

      Console.Write(lst[i] + " ");

    Console.WriteLine("\n");

    Console.WriteLine("Removing 2 elements");

    // Remove elements from the list.

    lst.Remove('F');

    lst.Remove('A');

    Console.WriteLine("Number of elements: " +

                       lst.Count);

    // Use foreach loop to display the list.

    Console.Write("Contents: ");

    foreach(char c in lst)

      Console.Write(c + " ");

    Console.WriteLine("\n");

    Console.WriteLine("Adding 20 more elements");

    // Add enough elements to force lst to grow.

    for(int i=0; i < 20; i++)

      lst.Add((char)('a' + i));

    Console.WriteLine("Current capacity: " +

                       lst.Capacity);

    Console.WriteLine("Number of elements after adding 20: " +

                       lst.Count);

    Console.Write("Contents: ");

    foreach(char c in lst)

      Console.Write(c + " ");

    Console.WriteLine("\n");

    // Change contents using array indexing.

    Console.WriteLine("Change first three elements");

    lst[0] = 'X';

    lst[1] = 'Y';

    lst[2] = 'Z';

    Console.Write("Contents: ");

    foreach(char c in lst)

      Console.Write(c + " ");

    Console.WriteLine();

    // Because of generic type-safety,

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