Introduction
The new .NET framework that Microsoft has recently released is quite
different than the framework that VB6 is based on. When I first started
working with VB.NET, the true Object Oriented Programming (OOP) threw me for a
loop. This guide will explain to you what OOP is, and how to build your
first program.
OOP has been around for a while, though never truly in VB until VB.NET.
But what is OOP, you ask? OOP is exactly what it says: Object Oriented
Programming. Each thing (class, button, text box, etc) that you use while
programming is an object. Back in the QBasic days, all programs ran top
down, or what you coded first was what happened first (I am grossly
simplifying). For example, when you coded the program to display a line of
text, or to draw a circle, it would draw a circle or display text in the order
that you coded it. In OOP, your code is attached to an object, and when an
event occurs to that object, then the appropriate code is executed. For
example, you create a button and attach code to the button to "fire" when
the button is clicked; the code will not "fire" or run until the button has
been clicked. Now the code that is ran when the button is clicked is
similar to the code back in the day before OOP, but is not quite the same.
The difference lies in the fact that the code in OOP is based on classes.
Now I know what you are asking, what is this class thing? A class is
exactly that, a thing. It could be anything, and in the case of VB.NET it
is everything. Let's say that there is a class called Book. Every
property that is associated with a book is encapsulated in its class. For
example, the total pages in the book is a property of the book, the color of the
book is another property, and if the book is hardback or not is another.
Let's take an example from VB.NET. A button in VB.NET is a class and an
object. This object has many properties. One such property is that
of the caption on the button, another is the color of the button, and another is
if the button is visible/accessible or not. Each of these properties of
the class can be accessed and changed (generally speaking). Now that we
have some of the very basic principals down, we can start by creating our very
first program.
Our First Project
In order for us to create our program, we must first open a new project we
can do this by clicking on the File menu option, then selecting new, then
project. This will bring up a form asking you what kind of project you
would like to create. For this project, we would like to make a Windows
Application in VB.Net. Select the folder called Visual Basic Projects, and
select Windows application. For this project, we will be calling our
program "Hello World." Select where you would like to place the
program that you will create, and when you have done all that, you screen should
look similar to the following graphic:
(Figure 1.1)
Now it is time for a basic tour around the screen. You will see a
pretty familiar menu system on the top of the screen. Don't be fooled
(maybe "note" would be more appropriate???), there are some very powerful
wizards enclosed in these menus, wizards that can save you hours of hard coding.
You will also see a toolbar on either side of the screen (depending on setup and
layout). You should also see a property bar to either side of the screen.
(Figure 1.2)
Take a moment to look around. After you feel a little more familiar
with the screen, we can start creating our new program.
From the toolbar, select windows forms, if it hasn't already been selected
by default. From this menu you can select many different objects that you
can add to your program. Scroll down the bar until you come to the
RichTextBox object. Click it. Now if you move your mouse over to the
form (it should have the name of Form1 on it) you will notice that the mouse
cursor has changed. Now like almost any windows application, just drag and
draw the object. If you make the object too small, that's okay, because
you can resize the image easily by dragging one of the white squares on the
outside of the image. After you have drawn (or added an object) you will
see the object created in your form. Now it is time to use the properties
bar. Select the TEXT option in the properties bar and change the text from
RichTextBox1 to Hello World. Click the form and you will see that the text
inside the RichTextBox object has changed to Hello World. Now we can also
do this with the form. Click the form, or select Form1 from the dropdown
box on the property bar, and change the text property to Hello World.
Now you should have a project that looks similar to figure 1.3.
(Figure 1.3)
Well we have a great looking project but it doesn't do anything.
Lets add a few buttons to add some functionality to our project. Once
again, go to the Toolbox bar. This time select Button from the options.
Draw the button onto the form, and then repeat the process until you have drawn
three buttons on to your form. Once you have completed drawing the
buttons, change the texts on all three buttons. Change button1's text to
Clear. Change button2's text to Hello World. And change
button3's text to Color. Now that you have completed that, we can start
coding. Double click the Clear button. When you double click any
object in a project, it will bring up the coding screen. Enter the
following code into the program:
RichTextBox1.Text = ""
Your coding screen should look as mine does in figure 1.4.
(Figure 1.4)
As I have indicated earlier, everything in VB.NET is an object of some sort,
and RichTextBox1 is no different. To access any property associated with
RichTextBox1, all you must do is call it by name, add a "." (period) and
then call its property by name, as is illustrated in the example above.
Lets examine the code a little closer. As we have just discussed,
the object RichTextBox1 can be referenced by calling it by name, along with any
one of its properties. When we have changed the RichTextBox1 text property
before to Hello World, we set its initial property value. The code attached to
the event of clicking button (Button1_Click) changes the initial RichTextBox1
text property from Hello World to nothing (hence the Clear text value for
button1). To test your code, click the play button (the triangle on the
menu bar). After a few moments, your project will appear. Click the
Clear button and notice that the text in the RichTextBox1 object disappears.
Close your program, and return to the design screen. We will now add code
to the other two buttons. Double click the Hello World Button, and access
the coding screen. Enter the following code into the program:
RichTextBox1.Text = "Hello World"
This will add the words Hello World back into the RichTextBox1 object.
Once again, we are accessing the RichTextBox1 object by calling it by name.
We are also access the RichTextBox1 text property in the same way as we did with
the Clear button code.
Click back to the Design screen and double click on the Color button.
The code for this button is similar to the other button's code, but we will be
accessing another class other than the RichTextBox1. Lets examine the code
that will go into this button:
RichTextBox1.SelectionColor = Color.Red
As you can see, we have called RichTextBox1 again, but this time we have
accessed its SelectionColor property. This property changes (or returns)
the color of selected text within the parent object (in this case RichTextBox1).
The difference in this code from the others is that we are setting the property
to a value from another class, other than a value (or empty value) that we code.
Color in this case is a class. On of its properties is red. So you
can see that we are going to set the Selected color in the RichTextBox1 to red.
Say we wanted to change the color to blue instead of red, in that case we would
set the RichTextBox1.SelectionColor = Color.Blue. The final coding screen
should look similar to that in figure (1.5)
(Figure 1.5)
Test your code in the same manor as before, but this time select some text
from the RichTextBox1 object and click color. If you don't have any text
due to clicking clear, click the Hello World button, or just type some of your
own into the rich text box.
Now that you have the general idea about objects and how to access their
properties, I suggest for you to practice on some of the other objects that are
found in the Toolbar.