Module 3. Workinig with Classes and Objects

Creating a Class

In the simple Program.cs, there is already a class defined called Program, which contain a method Main

Task: encapsulate all grade calculation process in a class to simplify code

Note: Every class/method should be within a namespace. If not in a namespace, then the code fall into global namespace, which is dangerous.

Adding State

Creating a class definition is easy

namespace GradeBook
{
    class Program
    {
        static void Main(string[] args)
        {
            var book = new Book();

            //...
        }
    }

    class Book
    {
        
    }
}

A class has 2 types of members:

State (data)
Behavior (methods)

Defining a Method

        public void AddGrade(double grade)
        {
            
        }

Add Field Definition to class to contain state/data

List<double> grades;

The field definition has to be explicitly in type.

Adding a Constructor

All created class need a constructor, so objects can be initialized.

Separate a class to a separate .cs file, as long as files are within same namespace, no need to use sth like #include

Check C# Classes and structs -> Constructors

Requiring Constructor Parameters

Access Modifier
Args in constructor
keyword: this
- It's an implicit variable that always available at all classes
- It's optional if there is no conflict. But useful when need specify this object

W/o correct Access Modifier, other programs will mess up code usage.

Access Modifier provide encapsulation:

public
private
internal
internal

By assigning Access Modifier to class member, we can set visibility of these members

Working with Static Members

Static member of class vs. Instance member of class:

Static Modifier: Declare class member with static, makes it belong to class itself rather than objects.
Non-static members are "instance member"

Once a class method is static, then the data it use should also be static (not of instance)

Be careful of using static.

static member e.g. Console.WriteLine(), double.MinValue