OO Programming in C# Computing Resources. COMP104-11S Teaching Staff. COMP104-11S Textbooks

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1 Computing Resources Official Lab: Computing Laboratory 5 (R G.12) Lecture 1 OO Programming in C# Robi Malik Microsoft Visual Studio 2008 is installed on the Windows computers in this lab. DEPARTMENT OF COMPUTER SCIENCE TARI ROROHIKO THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 4 COMP104-11S Teaching Staff Robi Malik Room G 2.03 robi@cs.waikato.ac.nz Tim Elphick Room R G.13 telphick@cs.waikato.ac.nz COMP104-11S Textbooks Douglas Bell, Mike Parr, C# for Students, Addison Wesley, Revised Edition, Joel Murach, Murach s C# Mike Murach & Associates, Inc., THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 2 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 5 COMP104-11S Timetable Lectures: Monday 12:00 14:00 K G.11 Wednesday 12:00 14:00 K G.11 Friday 12:00 14:00 K G.11 Supervised Labs: Weekdays 10:00 11:00 R G.12 COMP104-11S Moodle Course Home Page course/view.php?id=10464 Will contain: Up-to-date Information Lecture Notes and Assignment Handouts Online Quizzes Assignment Submission THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 3 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 6 1

2 COMP104-11S Assessment Internal Assessment Assignment 1 16% due Monday 10 January 2011 Assignment 2 16% due Monday 17 January 2011 Assignment 3 16% due Monday 24 January 2011 Test 16% held Friday 28 January 2011 Assignment 4 32% due Monday 14 February Online Quizzes 4% due Wednesdays Final Examination (35% minimum) Ratio 2:1 or 1:2 (whichever works in your favour) THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 7 C# Methods Scope Return type Method name private void button1_click (object sender, System.EventArgs e) Parameter list Body Methods can be called automatically in response to events directly by our program code The body is executed line by line THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 10 COMP104S Overview Object Oriented Programming with C# Graphical User Interfaces Object and Class Design Software Development Two Kinds of Variables Local Variables Declared in method body Lose their value when method exits. Instance Variables Declared in class body Keep their value across method calls Flagged with underscore by convention. int count(int n) int i = 0; i += n; class Ball private int x_; private int y_; THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 8 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 11 Today: Programming in C# C# programs consist of classes. The main class (typically called Form1) is generated automatically by Visual Studio. Other classes can be created by the programmer. class name Classes contain: body methods instance variables properties Classes: Naming Conventions public class MainWindow nouns upper case camel notation Methods: public void DrawImamge() verbs upper case camel notation in C# Variables: private int innerradius_ nouns (adjectives for Booleans) lower case camel notation instance variables flagged with underscore THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 9 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture

3 What is an Object? Observation: Real-world objects always have State Behaviour Definition: An object is a software bundle of variables (state) and related methods (behaviour). THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 13 Information Hiding Important: Instance variables are buried within the object. They cannot be accessed directly from outside. They are private. THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 16 What is an Object? What is a Message? Methods (behaviour) Instance variables (state) Means of communication between objects. If an object A wants another object B to perform one of its methods, then A sends an appropriate message to B. THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 14 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 17 Example: Bicycle Object Example: Sending a Message gears 10 mph gears (lowergear) brake 90 rpm cadence 5 th gear Me My bicycle THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 15 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture

4 What is a Class? Superclass and Subclass Definition: A class is a blueprint, or prototype, that defines the variables and the methods common to all objects of a certain kind. Bicycle Mountain Bike Superclass Subclass Inherits state and behaviour from superclass. May add new state and behaviour. May also override inherited behaviour. THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 19 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 22 Class and Instance Where are the Objects? Bicycle gears speed_ gears 10 mph brake brake cadence Class cadence My bicycle Instance THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 20 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 23 What is Inheritance? The Ball Class Bicycle A ball is a round object that moves. Responsibilities: Movement within a box Rendering Mountain Bike Racing Bike Tandem Bike THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 21 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture

5 Class Diagram for Ball Ball position_ speed_ diameter_ Move() Draw() Class name State / Instance Variables / Data Members Behaviour / Responsibilities / Methods Structure of a Class public class Ball // Instance Variables // Public Methods // Properties // Private Methods Class Name Upper case by convention. THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 25 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 28 Class Diagram for BallWorld Instance Variables BallWorld uses Ball position_ speed_ diameter_ Move() Draw() Instance Variables describe the state of an object Also called Data Members. Every object of the class has its own copy of the instance variables. Every object can have different values for its instance variables. THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 26 THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 29 Composition The simplest way of reusing code! Just place an object reference you want to use inside a new class. Best way of expressing has-a relationships. THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 27 Declaring Instance Variables //##################### //# Instance Variables private Point pos_; private Point speed_; private int diameter_; Scope Instance variables should be private so they cannot be accessed from outside of the class. Type Name Flagged with underscore by convention. THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture

6 Methods Methods describe the behaviour of objects. Public methods can be called by users of the class. They describe the interface of the class. Some methods may be private to represent auxiliary behaviour. Private methods can only be called by other methods of the same class. Constructors are a special type of method called to create objects of the class. THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 31 Another Class A list is an ordered collection of objects. [0] [1] [2] [3] Lists are parameterised by generic type: List<Ball> a list of balls List<float> a list of numbers List<List<int>> a list of lists THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 34 Scope Writing a Public Method Return Type Name Upper case by convention. public void Draw(Graphics graphics) Brush brush = new SolidBrush(Color.Red); graphics.fillellipse (brush, pos_.x, pos_.y, diameter_, diameter_); THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 32 Some List Code List<int> list = new List<int>(); list.add(1); list.add(0); list.add(4); int size = list.count; foreach (int i in list) MessageBox.Show(i); int secondelement = list[1]; list.removeat(1); THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 35 Scope Writing a Constructor Omit Return Type Class Name public Ball (int x, int y, int dx, int dy, int radius) pos_ = new Point(x, y); speed_ = new Point(dx, dy); diameter_ Matching = call: 2 * radius; Ball ball = new Ball(20, 25, 2, 2, 10); THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture 1 33 Reading C# for Students Chapter 10: Writing Classes pp Murach s C# 2008 Chapter 12: How to Create and Use Classes pp THE UNIVERSITY OF WAIKATO TE WHARE WANANGA O WAIKATO COMP104-11S Lecture