B – Starting With (Instances of) Classes

Overview

This topic introduces some of the basic syntax and grammar surrounding Object-Oriented Programming in C#. The following keywords are introduced. (Note that additional keywords from previous topics may also be present.)

• new
• char
• int
• double

This topic will also introduce the following grammars, syntax and language constructs. (Note that additional concepts from previous topics may also be present.)

• Method declaration syntax (instance methods)
• Object instantiation
• Instance method call syntax (with and without arguments)
• Class Field declaration syntax (member variables)
• Assignment statement syntax
• Accessing public fields in objects (storing & retrieving values)

Note that this package introduces the distinction between static and non-static methods. Static methods, also known as "class methods", are identified by the keyword static and must be qualified by the class name; for example, in the following method call Salutation is the name of the class and Greeting is a static method of that class.
Salutation.Greeting()

Non-static methods, also known as "instance methods", are identified by the absence of the static keyword and must be called by using an instance of the class (that is, an object). An example of calling an instance method would be
app.Greeting()
where the app is an instance of the Salutation class.

LOGs

At the end of this topic, you should be able to ...

OOP Basics

• Define the term "object" as used in OOP
• Describe the syntax of static and non-static method declarations
• Compare and contrast the syntax for method declarations (implementations) vs. method calls (for both static and non-static methods)
• Define the term "field" as used in OOP and give an example
• Compare and contrast instance and class members, for both methods and fields
• Identify the "member access operator" and explain it's purpose
• Create (instantiate) objects
• Distinguish between classes and objects in OOP
• Explain what is meant by the phrase “type extensibility” and how classes represent “complex” data types in OOP

General Programming Concepts and Terms

• List the three categories of simple information
• Define the term "intrinsic data type"
• Explain what an assignment statement is and how it works
• Compare and contrast the three categories of simple information with the complex types of information which classes represent
• Explain the advantages of using classes and objects instead of only using intrinsic data types