Lesson 4: Writing the Code in VB2022

Master event-driven programming and learn to write code that responds to user interactions

Key Takeaway

Visual Basic 2022 is an event-driven programming language. Your code responds to events triggered by user actions like clicking buttons or typing in textboxes. Mastering event handling is essential for creating interactive applications.

Welcome to Lesson 4 of our Visual Basic 2022 Tutorial! In this lesson, you'll learn how to write code that makes your applications respond to user interactions. We'll cover event-driven programming concepts, create event handlers, and explore practical examples that bring your UI to life.

Learning Objectives

Understand event-driven programming concepts
Write code for different events
Use message boxes for user feedback
Perform arithmetic operations
Work with form controls programmatically

4.1 The Concept of Event-Driven Programming

Visual Basic 2022 is an event-driven programming language, meaning code executes in response to events triggered by user actions like clicking a mouse, pressing keys, or selecting items from lists. Other events include form loading, mouse movements, and timer events.

Pro Tip

The most common events you'll use include Click for buttons, TextChanged for textboxes, and Load for forms.

1 Accessing Events

Every control on a form has a set of associated events. To view these events:

Double-click a control on the form to open the code window
View the default event at the top right of the code window
Click the default event dropdown to see all available events

2 Event Procedure Structure

All event procedures follow this basic structure:

EventStructure.vb

Private Sub ControlName_EventName(sender As Object, e As EventArgs) Handles ControlName.EventName
    ' Your code goes here
End Sub

The sender parameter refers to the object that raised the event, and e contains event-specific data.

Figure 4.1: Events associated with Form

Figure 4.2: Events associated with the Button control

4.2 Writing Your First Code

Let's start with simple examples that demonstrate how to write and execute code in VB2022.

FirstApp.vb

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        MsgBox("My First Visual Basic 2022 App", , "Welcome Message")
    End Sub
End Class

Output:

When you run this program, a message box displaying "My First Visual Basic 2022 App" will appear as soon as the form loads.

Figure 4.3: The message box output

Understanding MsgBox

The MsgBox function displays a message in a dialog box. The parameters are:

Message text
Buttons (optional - omitted here)
Title (optional)

Arithmetic.vb

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    MsgBox("2 + 5 = " & (2 + 5))
    MsgBox("10 - 3 = " & (10 - 3))
    MsgBox("4 × 6 = " & (4 * 6))
    MsgBox("20 ÷ 5 = " & (20 / 5))
End Sub

Output:

This example demonstrates basic arithmetic operations in VB2022. When the form loads, it will show four message boxes with different calculations.

Figure 4.4: Arithmetic operation result

Important Note

The & operator concatenates strings. Numeric operations are performed inside parentheses and converted to strings for display.

4.3 Practical Examples

Button Click Event

This example shows how to handle a button click event to change a label's text.

1 Implementation Steps

Add a Button control to your form (named Button1)
Add a Label control (named Label1)
Double-click Button1 to create the Click event handler

2 Code Example

ButtonClick.vb

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Label1.Text = "Button was clicked!"
    Label1.ForeColor = Color.Blue
    Label1.Font = New Font("Arial", 12, FontStyle.Bold)
End Sub

Behavior: When Button1 is clicked, the label text changes to "Button was clicked!", turns blue, and uses a bold Arial font.

Figure 4.5a: Before button click

Figure 4.5b: After button click

Text Input Processing

vb2022/vb2022images/Figure4.5a;png

This example demonstrates how to get user input from a TextBox and display it in a message box.

1 Implementation Steps

Add a TextBox control (named TextBox1)
Add a Button control (named Button2)
Double-click Button2 to create the Click event handler

2 Code Example

TextInput.vb

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    If String.IsNullOrEmpty(TextBox1.Text) Then
        MsgBox("Please enter your name!", MsgBoxStyle.Exclamation, "Input Required")
    Else
        MsgBox("Hello, " & TextBox1.Text & "! Welcome to VB2022.", MsgBoxStyle.Information, "Greeting")
    End If
End Sub

Behavior:

If TextBox1 is empty, shows an error message
If text is entered, shows a personalized greeting

Lesson Summary

In this lesson, we covered essential concepts for writing code in Visual Basic 2022:

Event-Driven Programming

VB2022 executes code in response to user-triggered events

Event Procedures

Structured as Private Sub ControlName_EventName(...) Handles ...

Message Boxes

Using MsgBox() to display information to users

Arithmetic Operations

Performing calculations with +, -, *, / operators

Control Interaction

Changing properties of controls like Labels and TextBoxes

These skills form the foundation for creating functional applications in VB2022. In the next lesson, we'll explore how to work with various controls in more depth.

Exercises

Practice what you've learned with these exercises:

Exercise 1: Simple Calculator

Create a program with:

Two TextBox controls for number input
Four Button controls (+, -, ×, ÷)
One Label to display results

Write code so that when a button is clicked, the corresponding arithmetic operation is performed on the two numbers, and the result is displayed in the Label.

Exercise 2: Personal Information Form

Create a form with:

Textboxes for first name, last name, and age
A "Submit" button

When the button is clicked:

Validate that all fields contain data
If valid, display a message: "Hello [First Name] [Last Name]. You are [Age] years old."
If invalid, show an appropriate error message

Exercise 3: Dynamic Control Properties

Create a program that allows users to:

Change a label's text using a TextBox and Button
Change a label's color using a ComboBox with color options
Toggle a label's visibility with a CheckBox

Next Lesson

Ready to learn how to work with different controls? Continue to Lesson 5: Working with Controls.

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