Chapter 5: Programming with C#

1. Microsoft® Visual C# 2008 Chapter 5: Programming with C#

2. Overview • Using Arrays • Using Collections • Using Exception Handling • Using Interfaces (optional) • Using Delegates and Events (optional)

3. Lesson: Using Arrays • 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

4. 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: • Single-dimensional, an array with the rank of one • Multidimensional, an array with a rank greater than one • Jagged, an array whose elements are arrays • Array methods

5. 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 Syntax type[] array-name; Example Int[] MyIntegerArray; • Instantiate to create • int[ ] numbers = new int[5]; • To create an array of type Object • object [ ] animals = new object [100];

6. How to Initialize and Access Array Members • Initializing an array int[] numbers = {10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0}; numbers[4] = 5; • Accessing array members string[] animal = {"Mouse", "Cat", "Lion"}; animal[1]= "Elephant"; string someAnimal = animal[2];

7. How to Iterate Through an Array Using the foreach Statement • Using foreach statement repeats the embedded statement(s) for each element in the array Syntax • foreach ( type identifier in expression ) • statement-block Examples • int[] numbers = {4, 5, 6, 1, 2, 3, -2, -1, 0}; • foreach (intiin numbers) { • Console.WriteLine(i); • }

8. How to Use Arrays as Method Parameters • Pass an array to a method • Use the params keyword to pass a variable number of arguments to a • method • public int Sum(paramsint[] list) { • int total = 0; • foreach ( inti in list ) { • total += i; • } • return total; • } • ... • // pe is the object providing Sum() • ... • int value = pe.Sum( 1, 3, 5, 7, 9, 11 );

9. How to Index an Object • Use this keyword, and get and setaccessors • public class Zoo { • private Animal[] theAnimals; • public Animal this[inti] { • get { • return theAnimals[i]; • } • set { • theAnimals[i] = value; • } • } • }

10. Practice: Using a foreach Statement with an Array Hands-on Practice • In this practice, you will create an array, populate it, and use the foreach statement to print out the values in the array

11. Practice (optional): Using an Indexer Hands-on Practice • In this practice, you will write an indexer for the Zoo class

12. Lesson: Using Collections • 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

13. What Are Lists, Queues, Stacks, and Hash Tables? • 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

14. How to Use the ArrayList Class • 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

15. How to Use Queues and Stacks • Queues: first-in, first-out • Enqueue places objects in the queue • Dequeue removes objects from the queue • Stacks: last-in, first-out • Push places objects on the stack • Pop removes objects from the stack • Count gets the number of objects contained in a stack or queue

16. How to Use Hash Tables • A hash table is a data structure that associates a key with an object, for • rapid retrieval 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#” Key Object

17. Practice: Creating and Using Collections Hands-on Practice • In this practice, you will use the ArrayList class

18. Lesson: Using Exception Handling • How to Use Exception Handling • How to Throw Exceptions

19. How to Use Exception Handling • Exception handling syntax • try { • // suspect code • } • catch { • // handle exceptions • } • finally { • // always do this • }

20. How to Throw Exceptions • Throw keyword • Exception handling strategies • Exception types • The predefined common language runtime exception classes • Example: ArithmeticException, FileNotFoundException • User-defined exceptions

21. Practice: Using Exception Handling Hands-on Practice • In this practice, you will use throw and catch an exception

22. Lesson: Using Interfaces (optional) • 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

23. What Is an Interface? An interface: • 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

24. How to Use an Interface • An interface defines the same functionality and behavior to unrelated • classes • Declare an interface • Implement an interface • interface ICarnivore { • boolIsHungry { get; } • Animal Hunt(); • void Eat(Animal victim); • }

25. How to Work with Objects That Implement Interfaces • is • if ( anAnimalisICarnivore ) { • ICarnivoremeatEater = (ICarnivore) anAnimal; • Animal prey = meatEater.Hunt(); • meatEater.Eat( prey ); • } • as • ICarnivoremeatEater = anAnimalasICarnivore; • if ( meatEater != null ) { • Animal prey = meatEater.Hunt(); • meatEater.Eat( prey ); • } • // is and as with an object • if ( prey is Antelope ) { ... }

26. How to Inherit Multiple Interfaces • Class Chimpanzee : Animal, ICarnivore, IHerbivore { … } • Interfaces should describe a type of behavior • Examples: • Lion is-a-kind-of Animal; Lion has Carnivore behavior • Shark is-a-kind-of Animal; has Carnivore behavior • Derive Lion and Shark from abstract class Animal • Implement Carnivore behavior in an Interface

27. Interfaces and the .NET Framework • Allows you to make your objects behave like .NET Framework objects • Example: Interfaces used by Collection classes • ICollection, IComparer, IDictionary, IDictionary Enumerator, • IEnumerable, IEnumerator, IHashCodeProvider, IList • public class Zoo : IEnumerable { • . . . • public IEnumeratorGetEnumerator() { • return (IEnumerator)new ZooEnumerator( • this ); • }

28. Practice: Using Interfaces Hands-on Practice • In this practice, you will implement the ICloneable interface

29. Lesson: Using Delegates and Events • How to Create a Delegate • What Is an Event? • How to Write an Event Handler

30. How to Create a Delegate Zoo Keeper 1 Schedule lion CheckClaws Zoo Keeper 1 Schedule lion CheckClaws Medical Center ScheduleApointment Calls ProcessNextPatient Delegate AppointmentType Lion CheckClaws Antelope CheckHooves

31. What Is an Event? • Mouse and keyboard MouseDown, MouseUp, MouseMove, MouseEnter, MouseLeave, MouseHover KeyPress, KeyDown, KeyUp • Property FontChanged SizeChanged CursorChanged

32. How to Write an Event Handler • Declare events using delegates • System.EventHandler is declared as a delegate • button1.Click += new System.EventHandler(button1_Click); • Event handler is called when the event occurs • EventArgs parameter contains the event data • private void button1_Click(object sender, System.EventArgs e) { • MessageBox.Show( e.ToString() ); • }

33. Practice: Declaring and Calling a Delegate Hands-on Practice • In this practice, you will create and use a delegate

34. Review • Using Arrays • Using Collections • Using Exception Handling • Using Interfaces • Using Delegates and Events

35. Lab 5:1: Using Arrays • Exercise 1: Sorting Numbers in an Array

36. Lab 5.2 (optional): Using Indexers and Interfaces • Exercise 1: Writing the Check Pick-up Application • Exercise 2: Using Interfaces

37. Lab 5.3 (optional): Using Delegates and Events • Exercise 1: Working with Events and Delegates