Chapter 5: Programming with C#

Chapter 5: Programming with C#

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Microsoft®

Visual C# 2008

Overview

Using ArraysUsing CollectionsUsing Exception Handling Using Interfaces (optional)Using Delegates and Events (optional)

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Lesson: Using Arrays

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What Is an Array?

How to Create an Array

How to Initialize and Access Array Members

How to Iterate Through an Array Using the foreach

Statement

How to Use Arrays as Method Parameters

How to Index an Object

What Is an Array?

A data structure that contains a number of variables called elements of

the array

All of the array elements must be of the same type

Arrays are zero indexed

Arrays are objects

Arrays can be:

o Single-dimensional, an array with the rank of one

o Multidimensional, an array with a rank greater than one

o Jagged, an array whose elements are arrays

Array methods

How to Create an Array

Declare the array by adding a set of square brackets to end of the variable

type of the individual elements

Instantiate to create

o int[ ] numbers = new int[5];

To create an array of type Object

o object [ ] animals = new object [100];

Int[] MyIntegerArray;

type[] array-name;

Syntax

Example

How to Initialize and Access Array Members

string[] animal = {"Mouse", "Cat", "Lion"};

animal[1]= "Elephant";

string someAnimal = animal[2];

int[] numbers = {10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0};

numbers[4] = 5;

Initializing an array

Accessing array members

How to Iterate Through an Array Using the foreach Statement

int[] numbers = {4, 5, 6, 1, 2, 3, -2, -1, 0};

foreach (int i in numbers) {

Console.WriteLine(i);

}

Using foreach statement repeats the embedded statement(s) for each

element in the array

foreach ( type identifier in expression ) statement-block

Syntax

Examples

How to Use Arrays as Method Parameters

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Pass an array to a method

Use the params keyword to pass a variable number of arguments to a

method

public int Sum(params int[] list) {int total = 0;foreach ( int i in list ) {

total += i;}return total;

}...// pe is the object providing Sum()...int value = pe.Sum( 1, 3, 5, 7, 9, 11 );

How to Index an Object

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Use this keyword, and get and set accessors

public class Zoo {private Animal[] theAnimals;public Animal this[int i] {

get {return theAnimals[i];

}set {

theAnimals[i] = value;}

}}

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Practice: Using a foreach Statement with an Array

In this practice, you will create an array, populate it, and use the foreach statement to print out the values in the array

Hands-on Practice

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Practice (optional): Using an Indexer

In this practice, you will write an indexer for the Zoo class

Hands-on Practice

Lesson: Using Collections

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What Are Lists, Queues, Stacks, and Hash Tables?

How to Use the ArrayList Class

How to Use Queues and Stacks

How to Use Hash Tables

What Are Lists, Queues, Stacks, and Hash Tables?

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Lists, queues, stacks, and hash tables are common ways to manage data

in an application

List: A collection that allows you access by index

Example: An array is a list; an ArrayList is a list

Queue: First-in, first-out collection of objects

Example: Waiting in line at a ticket office

Stack: Last-in-first-out collection of objects

Example: A pile of plates

Hash table: Represents a collection of associated keys and

values

organized around the hash code of the key

Example: A dictionary

How to Use the ArrayList Class

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ArrayList does not have a fixed size; it grows as needed

Use Add(object) to add an object to the end of the ArrayList

Use [] to access elements in the ArrayList

Use TrimToSize() to reduce the size to fit the number of elements in the ArrayList

Use Clear to remove all the elements

Can set the capacity explicitly

How to Use Queues and Stacks

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Queues: first-in, first-out

o Enqueue places objects in the queue

o Dequeue removes objects from the queue

Stacks: last-in, first-out

o Push places objects on the stack

o Pop removes objects from the stack

o Count gets the number of objects contained in a stack or queue

How to Use Hash Tables

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Book techBook = new Book("Inside C#", 0735612889);

// ...

public Hashtable bookList;

//

bookList.Add(0735612889, techBook);

//

Book b = (Book) bookList[0735612889];

// b’s title is "Inside C#”

A hash table is a data structure that associates a key with an object, for rapid retrieval

Key Object

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Practice: Creating and Using Collections

In this practice, you will use the ArrayList class

Hands-on Practice

Lesson: Using Exception Handling

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How to Use Exception Handling

How to Throw Exceptions

How to Use Exception Handling

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Exception handling syntax

try {

// suspect code

}

catch {

// handle exceptions

}

finally {

// always do this

}

How to Throw Exceptions

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Throw keyword

Exception handling strategies

Exception types

The predefined common language runtime exception classes

Example: ArithmeticException, FileNotFoundException

User-defined exceptions

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Practice: Using Exception Handling

In this practice, you will use throw and catch an exception

Hands-on Practice

Lesson: Using Interfaces (optional)

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What Is an Interface?

How to Use an Interface

How to Work with Objects That Implement Interfaces

How to Inherit Multiple Interfaces

Interfaces and the .NET Framework

What Is an Interface?

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Is a reference type that defines a contract

Specifies the members that must be supplied by classes or

interfaces that implement the interface

Can contain methods, properties, indexers, events

Does not provide implementations for the members

Can inherit from zero or more interfaces

An interface:

How to Use an Interface

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interface ICarnivore {

bool IsHungry { get; }

Animal Hunt();

void Eat(Animal victim);

}

An interface defines the same functionality and behavior to unrelated

classes

Declare an interface

Implement an interface

How to Work with Objects That Implement Interfaces

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if ( anAnimal is ICarnivore ) {ICarnivore meatEater = (ICarnivore) anAnimal;Animal prey = meatEater.Hunt();meatEater.Eat( prey );

}

is

ICarnivore meatEater = anAnimal as ICarnivore;if ( meatEater != null ) {

Animal prey = meatEater.Hunt();meatEater.Eat( prey );

}

as

// is and as with an objectif ( prey is Antelope ) { ... }

How to Inherit Multiple Interfaces

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Interfaces should describe a type of behavior

Examples:

o Lion is-a-kind-of Animal; Lion has Carnivore behavior

o Shark is-a-kind-of Animal; has Carnivore behavior

o Derive Lion and Shark from abstract class Animal

o Implement Carnivore behavior in an Interface

Class Chimpanzee : Animal, ICarnivore, IHerbivore { … }

Interfaces and the .NET Framework

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Allows you to make your objects behave like .NET Framework objects

Example: Interfaces used by Collection classes

o ICollection, IComparer, IDictionary, IDictionary Enumerator,

o IEnumerable, IEnumerator, IHashCodeProvider, IList

public class Zoo : IEnumerable {

. . .

public IEnumerator GetEnumerator() {

return (IEnumerator)new ZooEnumerator(

this );

}

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Practice: Using Interfaces

In this practice, you will implement the ICloneable interface

Hands-on Practice

Lesson: Using Delegates and Events

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How to Create a Delegate

What Is an Event?

How to Write an Event Handler

How to Create a Delegate

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Medical CenterScheduleApointment

CallsProcessNextPatient

DelegateAppointmentType

Zoo Keeper 1Schedule lion CheckClaws

Zoo Keeper 1Schedule lion CheckClaws

AntelopeCheckHooves

LionCheckClaws

What Is an Event?

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Mouse and keyboard

MouseDown,MouseUp,MouseMove,MouseEnter,MouseLeave,MouseHover

KeyPress, KeyDown, KeyUp

Property

FontChangedSizeChangedCursorChanged

How to Write an Event Handler

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Declare events using delegateso System.EventHandler is declared as a delegate

button1.Click += new System.EventHandler(button1_Click);

Event handler is called when the event occurso EventArgs parameter contains the event data

private void button1_Click(object sender, System.EventArgs e) {MessageBox.Show( e.ToString() );

}

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Practice: Declaring and Calling a Delegate

In this practice, you will create and use a delegate

Hands-on Practice

Review

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Using Arrays

Using Collections

Using Exception Handling

Using Interfaces

Using Delegates and Events

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Lab 5:1: Using Arrays

Exercise 1: Sorting Numbers in an Array

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Lab 5.2 (optional): Using Indexers and Interfaces

Exercise 1: Writing the Check Pick-up Application Exercise 2: Using Interfaces

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Lab 5.3 (optional): Using Delegates and Events

Exercise 1: Working with Events and Delegates