Introduction to programming using C# Question 1 An object is a ___ of a class. Property object method instantiation QUESTION 2 Fields within a class should be public. True False QUESTION 3 Properties or instance methods, within a class, should be public. True False QUESTION 4 How many arguments can be used in a Constructor header? 1 10 Any amount. 0 QUESTION 5 The default constructor both none of these sets numeric fields to 0 has empty parameters 10 points Saved QUESTION 6 Assume that you have created a class named Student with a constructor defined as Student(int age). Which of the following overloaded constructors could coexist with the Chair constructor without ambiguity? none of these Student(int age, string name) Student(int age) both QUESTION 7 A collection of methods that can be used by any class, as long as the class provides a definition to override the collection's definitions is a class a superclass an interface a template QUESTION 8 When you create a class and want to include the capability to compare its objects so they can use the Array.Sort() or Array.BinarySearch() method, you must Use the CompareTo() Method Create a destructor Create a constructor Use the IComparable () method QUESTION 9 You can use the instance variable field as the identifier for an instance method. Example: private int age; public int age { get; set; } True False QUESTION 10 Arrays can hold references to objects. True False Module Nine Class Concepts Concepts / Vocabulary • Classes can be considered application • Instance Variables (known as fields) programs that contain a Main () hold object attributes or data method. components for a class. • Classes can hold objects that can be • Instance Methods: instantiated by another class. • Associated with objects and every Everything is essentially an object or a instance of the class will have the same member of another class because methods. objects are one property or one element of a class. Concepts / Vocabulary • Class Header: • Creating a Class: • Like methods, it has an optional access class ClassName modifier. A method default access modifier is private but a class default is { internal. • We us the keyword class to create a class, followed by an identifier or name for the class. • Also like a method, we can use other access modifiers such as public, protected, internal and private. // Instance variables and // methods can go inside //the braces. } Concepts / Vocabulary Module Nine Instance Variables and Methods Concepts / Vocabulary When a class is created, we also define the attributes and properties of the class. This would include the variables or fields of a class, properties or objects of the class and methods. When we use private fields within a class, it is considered information hiding. The fields of a class have their own set of access modifiers that include: new, public, protected, internal, private, static, readonly, and write. This allows you to control outside access to data by controlling private data from a public method. *Most fields will be private because they offer the highest level of security. Although not always the case, it would be good to make the class methods public. Concepts / Vocabulary We are able to use the variable idNumber even though it is private because we made the method public. So we can pull a private source from a public source and is why we make methods public. You can use the variable with better security this way. Concepts / Vocabulary • Has-a Relationship: • Defines the instance in which a class has objects of another class. • Composition: • Using an object within an object. • If this was a bank program, you would have a bank account class buy you would also have a class for actual customers that use objects from the bank account class. Module Nine Creating Objects Concepts / Vocabulary • Creating an Object: • When you create or declare a class, it does not contain or come pre-loaded with objects. All objects must be created. • To create an object we must: • 1) Declare an object type and a name (identifier). • 2) Create the object. • Reference Type: • The identifier we use for the object is how we reference its location or memory address. • When we create an object we can call its constructor. Concepts / Vocabulary • Class Object Example: Employee bob = new Employee (); Bob.WelcomeMsg(); • Passing Objects to Methods: • You can pass objects to methods just like other data types: • Example: (in main) Module Nine Properties Concepts / Vocabulary • Property: • The member of a class that provides access to a field. A Get and Set will be defined for setting and retrieving field information. • The setter and getter are known as accessors. The “set” sets the value for a field and the “get” returns the stored value of a field. • Properties are linked to an object using the “.”. • Ex. student.Age; • Field Example: • private int age; • Property Example: Concepts / Vocabulary • Auto-Implemented Property: • The implementation or the set/get are automatically created for you. You do not need to declare the field that corresponds with the property. Class Student { public int Age (get; set;) public string Name (get; set;) } Module Nine This reference and public/private data Concepts / Vocabulary • Why care about the Accessibility? • When Programming, data should be hidden whenever possible, you never really want information to be public if you can help it. Instead, information should be accessed by accessors. • Public data fields can be used when all the objects of a class contain the same value. • You can create a constant variable with a class and it will always be static or it will always belong to the entire class, rather than a particular instance. Concepts / Vocabulary • Understanding the “this” Reference • The This reference is an implicitly passed reference. • It tells the method which instance or “scenario” of the class we are going to use. • You can also pass a parameter to a this.reference. Module Ten Using Contructors Concepts / Vocabulary • Constructors: • A special method that instantiates an object. There is a default constructor that automatically supplies a constructor with no parameters. • The default values of an object are initialized with a default constructor. • Book book1 = new Book(); • A default constructor takes no arguments; however, you are able to set information directly into them. • public Book() { ReaderName = “Nicole”; } Concepts / Vocabulary • Passing Parameters: • You can create constructors that receive different arguments. In fact, you can create several constructors to handle different circumstances. public Book () { ReaderName = Nicole; } ------------------------------------------public Book (string name) { ReaderName = name; } Concepts / Vocabulary • Overloading Constructors: • C# provides a default constructor even if you do not provide your own. • That being said, you can overload any constructor and you can write as many constructors as you want—however, beware redundancy. Module Ten Object Initializers Concepts / Vocabulary • Initializers: • Gives the programmer the ability to assign vales to object properties (which in return their fields) without calling the constructor, or passing a parameter. • *Requires a default constructor within the class. • Example: Student aStudent = new Student (StudentAge = 25); Concepts / Vocabulary • Benefits: • Allows you to create multiple objects with different initial assignments. • This means you do not need to worry about overloading multiple constructors. • Example: • Class Student { public int Age { get; set; } • It also allows you to create objects with different starting values. public string Name { get; set; } public int Id { get; set; } public Student() { Age = 25; Name = Nicole; Id = 2130498; } } Module Ten Overloading Operators Concepts / Vocabulary • Overloading Operators: • Allows you to use arithmetic symbols with an object. • Unary Operators: • +, -, !, ++, --, true, false • Binary Operators: • +, -, *, /, %, &, |, ==, !=, >, =,
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