C# 2008 Programmer's Reference

Chapter 4. Classes and Objects

One of the most important topics in C# programming — in fact, the cornerstone of .NET development — is classes and objects.

Classes are essentially templates from which you create objects. In C# .NET programming, everything you deal with involves classes and objects. This chapter assumes that you already have a basic grasp of object-oriented programming. It tackles:

• How to define a class

• How to create an object from a class

• The different types of members in a class

• The root of all objects — System.Object

Classes

Everything you encounter in .NET in based on classes. For example, you have a Windows Forms application containing a default form called Form1. Form1 itself is a class that inherits from the base class System.Windows.Forms.Form, which defines the basic behaviors that a Windows Form should exhibit:

using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Project1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
    }
}

Within the Form1 class, you code in your methods. For example, to display a "Hello World" message when the form is loaded, add the following statement in the Form1_Load() method:

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        protected override void OnLoad(EventArgs e)
        {
            MessageBox.Show("Hello World!");
        }
    }

The following sections walk you through the basics of defining your own class and the various members you can have in ...