.NET VB.NET Basics

Introduction

Visual Basic .NET (VB.NET) is a high-level, object-oriented programming language implemented on the .NET Framework. As part of the .NET family, it offers a user-friendly approach to building Windows applications, web services, and more. Originally designed as a successor to the classic Visual Basic language, VB.NET has evolved into a powerful tool that combines the simplicity of Visual Basic's syntax with the robust features of the .NET platform.

In this guide, we'll explore the fundamental elements of VB.NET programming, from basic syntax to creating simple applications. If you're new to programming or transitioning from another language, VB.NET's readable syntax makes it an excellent starting point for your coding journey.

Setting Up Your Environment

Before diving into VB.NET programming, you'll need to set up your development environment:

1. Visual Studio: Microsoft's Visual Studio is the recommended IDE (Integrated Development Environment) for VB.NET development. You can download Visual Studio Community Edition for free from Microsoft's website.

2. .NET Framework/.NET Core: Visual Studio includes the necessary .NET components, but ensure you select the ".NET desktop development" workload during installation.

VB.NET Syntax Fundamentals

Your First VB.NET Program

Let's start with the traditional "Hello World" program to understand the basic structure of a VB.NET application:

vb

Module Program
    Sub Main()
        Console.WriteLine("Hello, World!")
        Console.ReadLine() ' Keeps the console window open
    End Sub
End Module

Output:

Hello, World!

Let's break down what's happening here:

• Module Program declares a new module named "Program"
• Sub Main() is the entry point of the application
• Console.WriteLine() writes a line of text to the console
• End Sub marks the end of the Main subroutine
• End Module marks the end of the module

Comments

Comments in VB.NET allow you to add explanatory notes to your code:

vb

' This is a single-line comment

' Multi-line comments use the apostrophe on each line
' like this
' and this

REM This is another way to write comments (legacy style)

Variables and Data Types

VB.NET is a strongly-typed language, offering various data types to store different kinds of data:

vb

Module Variables
    Sub Main()
        ' Declaring variables with explicit data types
        Dim age As Integer = 25
        Dim name As String = "John Doe"
        Dim isActive As Boolean = True
        Dim salary As Double = 55000.75
        
        ' Variable with type inference (compiler determines the type)
        Dim temperature = 98.6 ' Inferred as Double
        
        ' Output
        Console.WriteLine("Name: " & name)
        Console.WriteLine("Age: " & age)
        Console.WriteLine("Active: " & isActive)
        Console.WriteLine("Salary: $" & salary)
        Console.WriteLine("Temperature: " & temperature & "°F")
        
        Console.ReadLine()
    End Sub
End Module

Output:

Name: John Doe
Age: 25
Active: True
Salary: $55000.75
Temperature: 98.6°F

Common Data Types

Data Type	Description	Example
Integer	Whole numbers	Dim count As Integer = 10
Long	Large whole numbers	Dim population As Long = 7800000000
Single	Single-precision floating-point	Dim weight As Single = 65.5F
Double	Double-precision floating-point	Dim pi As Double = 3.14159265359
Decimal	High-precision decimal values	Dim amount As Decimal = 1234.5678D
String	Text	Dim message As String = "Hello"
Boolean	True/False values	Dim isCompleted As Boolean = False
Date	Date and time	Dim today As Date = Date.Now
Char	Single character	Dim grade As Char = "A"c
Object	Generic object reference	Dim something As Object = 42

Basic Input and Output

VB.NET provides several ways to interact with users through input and output:

vb

Module IOExample
    Sub Main()
        ' Output
        Console.WriteLine("What is your name?")
        
        ' Input
        Dim userName As String = Console.ReadLine()
        
        ' Processing and output
        Console.WriteLine("Hello, " & userName & "! Welcome to VB.NET programming.")
        
        ' Formatting output
        Dim currentDate As Date = Date.Now
        Console.WriteLine("Today is {0:d} and the time is {0:t}", currentDate)
        
        ' Using string interpolation (.NET 6 and later)
        Console.WriteLine($"The date is {currentDate:yyyy-MM-dd}")
        
        Console.ReadLine()
    End Sub
End Module

Sample Output:

What is your name?
Alice
Hello, Alice! Welcome to VB.NET programming.
Today is 10/12/2023 and the time is 14:30
The date is 2023-10-12

Control Structures

Conditional Statements

If-Then-Else

vb

Module ConditionalExample
    Sub Main()
        Console.Write("Enter your age: ")
        Dim age As Integer = Integer.Parse(Console.ReadLine())
        
        If age < 18 Then
            Console.WriteLine("You are a minor.")
        ElseIf age >= 18 And age < 65 Then
            Console.WriteLine("You are an adult.")
        Else
            Console.WriteLine("You are a senior citizen.")
        End If
        
        Console.ReadLine()
    End Sub
End Module

Select Case (Switch)

vb

Module SelectCaseExample
    Sub Main()
        Console.Write("Enter a day number (1-7): ")
        Dim dayNum As Integer = Integer.Parse(Console.ReadLine())
        
        Select Case dayNum
            Case 1
                Console.WriteLine("Sunday")
            Case 2
                Console.WriteLine("Monday")
            Case 3
                Console.WriteLine("Tuesday")
            Case 4
                Console.WriteLine("Wednesday")
            Case 5
                Console.WriteLine("Thursday")
            Case 6
                Console.WriteLine("Friday")
            Case 7
                Console.WriteLine("Saturday")
            Case Else
                Console.WriteLine("Invalid day number")
        End Select
        
        Console.ReadLine()
    End Sub
End Module

Loops

For Loop

vb

Module ForLoopExample
    Sub Main()
        ' Basic For loop
        Console.WriteLine("Counting from 1 to 5:")
        For i As Integer = 1 To 5
            Console.WriteLine(i)
        Next
        
        ' For loop with Step
        Console.WriteLine("Even numbers from 2 to 10:")
        For j As Integer = 2 To 10 Step 2
            Console.WriteLine(j)
        Next
        
        Console.ReadLine()
    End Sub
End Module

Output:

Counting from 1 to 5:
1
2
3
4
5
Even numbers from 2 to 10:
2
4
6
8
10

While Loop

vb

Module WhileLoopExample
    Sub Main()
        Dim count As Integer = 1
        
        While count <= 5
            Console.WriteLine("Count is: " & count)
            count += 1
        End While
        
        Console.ReadLine()
    End Sub
End Module

Output:

Count is: 1
Count is: 2
Count is: 3
Count is: 4
Count is: 5

Do Loop

vb

Module DoLoopExample
    Sub Main()
        ' Do While - checks condition before execution
        Dim i As Integer = 1
        Do While i <= 3
            Console.WriteLine("Do While: " & i)
            i += 1
        Loop
        
        ' Do Until - loops until condition becomes true
        Dim j As Integer = 1
        Do Until j > 3
            Console.WriteLine("Do Until: " & j)
            j += 1
        Loop
        
        ' Do Loop While - checks condition after execution
        Dim k As Integer = 1
        Do
            Console.WriteLine("Do Loop While: " & k)
            k += 1
        Loop While k <= 3
        
        Console.ReadLine()
    End Sub
End Module

Output:

Do While: 1
Do While: 2
Do While: 3
Do Until: 1
Do Until: 2
Do Until: 3
Do Loop While: 1
Do Loop While: 2
Do Loop While: 3

Working with Arrays and Collections

Arrays

Arrays store multiple values of the same data type:

vb

Module ArrayExample
    Sub Main()
        ' Declare and initialize an array
        Dim fruits() As String = {"Apple", "Banana", "Cherry", "Date", "Elderberry"}
        
        ' Access array elements
        Console.WriteLine("The first fruit is: " & fruits(0))
        Console.WriteLine("The third fruit is: " & fruits(2))
        
        ' Get array length
        Console.WriteLine("Number of fruits: " & fruits.Length)
        
        ' Iterate through array
        Console.WriteLine("All fruits:")
        For Each fruit As String In fruits
            Console.WriteLine("- " & fruit)
        Next
        
        ' Multi-dimensional array
        Dim matrix(,) As Integer = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}
        
        Console.WriteLine("Element at position (1,2): " & matrix(1, 2)) ' Outputs 6
        
        Console.ReadLine()
    End Sub
End Module

Collections

VB.NET provides several collection types for more flexible data management:

vb

Imports System.Collections.Generic

Module CollectionsExample
    Sub Main()
        ' List (dynamic array)
        Dim numbers As New List(Of Integer)
        numbers.Add(10)
        numbers.Add(20)
        numbers.Add(30)
        
        Console.WriteLine("List count: " & numbers.Count)
        Console.WriteLine("Second number: " & numbers(1))
        
        ' Dictionary (key-value pairs)
        Dim capitals As New Dictionary(Of String, String)
        capitals.Add("USA", "Washington D.C.")
        capitals.Add("UK", "London")
        capitals.Add("France", "Paris")
        
        Console.WriteLine("Capital of France: " & capitals("France"))
        
        ' Checking if key exists
        If capitals.ContainsKey("Japan") Then
            Console.WriteLine("Capital of Japan: " & capitals("Japan"))
        Else
            Console.WriteLine("Japan is not in the dictionary.")
        End If
        
        Console.ReadLine()
    End Sub
End Module

Functions and Subroutines

VB.NET offers two types of procedures: functions (which return values) and subroutines (which don't):

vb

Module ProceduresExample
    ' Subroutine (does not return a value)
    Sub PrintWelcome(name As String)
        Console.WriteLine("Welcome, " & name & "!")
    End Sub
    
    ' Function (returns a value)
    Function CalculateArea(length As Double, width As Double) As Double
        Return length * width
    End Function
    
    ' Function with optional parameters
    Function FormatName(firstName As String, lastName As String, Optional includeMiddle As Boolean = False, Optional middleName As String = "") As String
        If includeMiddle AndAlso middleName <> "" Then
            Return firstName & " " & middleName & " " & lastName
        Else
            Return firstName & " " & lastName
        End If
    End Function
    
    Sub Main()
        ' Calling a subroutine
        PrintWelcome("Developer")
        
        ' Calling a function
        Dim area As Double = CalculateArea(5.5, 3.2)
        Console.WriteLine("The area is: " & area & " square units")
        
        ' Optional parameters
        Dim fullName1 As String = FormatName("John", "Doe")
        Dim fullName2 As String = FormatName("Jane", "Smith", True, "Elizabeth")
        
        Console.WriteLine(fullName1)
        Console.WriteLine(fullName2)
        
        Console.ReadLine()
    End Sub
End Module

Output:

Welcome, Developer!
The area is: 17.6 square units
John Doe
Jane Elizabeth Smith

Error Handling

VB.NET provides a robust error-handling system using Try-Catch blocks:

vb

Module ErrorHandlingExample
    Sub Main()
        ' Basic Try-Catch
        Try
            Console.Write("Enter a number to divide 100 by: ")
            Dim divisor As Double = Double.Parse(Console.ReadLine())
            Dim result As Double = 100 / divisor
            Console.WriteLine("Result: " & result)
        Catch ex As DivideByZeroException
            Console.WriteLine("Error: Cannot divide by zero.")
        Catch ex As FormatException
            Console.WriteLine("Error: Please enter a valid number.")
        Catch ex As Exception
            Console.WriteLine("An unexpected error occurred: " & ex.Message)
        Finally
            Console.WriteLine("This code always executes, whether there was an error or not.")
        End Try
        
        Console.ReadLine()
    End Sub
End Module

Practical Example: Simple Calculator Application

Let's combine what we've learned into a simple calculator application:

vb

Module CalculatorApp
    Function Add(a As Double, b As Double) As Double
        Return a + b
    End Function
    
    Function Subtract(a As Double, b As Double) As Double
        Return a - b
    End Function
    
    Function Multiply(a As Double, b As Double) As Double
        Return a * b
    End Function
    
    Function Divide(a As Double, b As Double) As Double
        If b = 0 Then
            Throw New DivideByZeroException("Cannot divide by zero")
        End If
        Return a / b
    End Function
    
    Sub Main()
        Console.WriteLine("==== Simple Calculator ====")
        
        Try
            ' Get first number
            Console.Write("Enter first number: ")
            Dim num1 As Double = Double.Parse(Console.ReadLine())
            
            ' Get second number
            Console.Write("Enter second number: ")
            Dim num2 As Double = Double.Parse(Console.ReadLine())
            
            ' Get operation
            Console.WriteLine("Select operation:")
            Console.WriteLine("1. Add")
            Console.WriteLine("2. Subtract")
            Console.WriteLine("3. Multiply")
            Console.WriteLine("4. Divide")
            Console.Write("Enter choice (1-4): ")
            Dim operation As Integer = Integer.Parse(Console.ReadLine())
            
            Dim result As Double
            
            ' Perform calculation based on operation
            Select Case operation
                Case 1
                    result = Add(num1, num2)
                    Console.WriteLine($"{num1} + {num2} = {result}")
                Case 2
                    result = Subtract(num1, num2)
                    Console.WriteLine($"{num1} - {num2} = {result}")
                Case 3
                    result = Multiply(num1, num2)
                    Console.WriteLine($"{num1} × {num2} = {result}")
                Case 4
                    result = Divide(num1, num2)
                    Console.WriteLine($"{num1} ÷ {num2} = {result}")
                Case Else
                    Console.WriteLine("Invalid operation selected")
            End Select
            
        Catch ex As FormatException
            Console.WriteLine("Error: Please enter valid numbers.")
        Catch ex As DivideByZeroException
            Console.WriteLine("Error: " & ex.Message)
        Catch ex As Exception
            Console.WriteLine("An unexpected error occurred: " & ex.Message)
        End Try
        
        Console.WriteLine("Press Enter to exit.")
        Console.ReadLine()
    End Sub
End Module

This calculator demonstrates many of the concepts we've covered: functions, input/output, error handling, control structures, and type conversion.

Object-Oriented Programming Basics

VB.NET is a fully object-oriented language. Here's a simple example of a class:

vb

' Class definition
Public Class Person
    ' Properties
    Public Property FirstName As String
    Public Property LastName As String
    Public Property Age As Integer
    
    ' Constructor
    Public Sub New(firstName As String, lastName As String, age As Integer)
        Me.FirstName = firstName
        Me.LastName = lastName
        Me.Age = age
    End Sub
    
    ' Method
    Public Function GetFullName() As String
        Return FirstName & " " & LastName
    End Function
    
    ' Function to check if person is adult
    Public Function IsAdult() As Boolean
        Return Age >= 18
    End Function
End Class

Module OOPExample
    Sub Main()
        ' Create an instance of the Person class
        Dim person1 As New Person("Jane", "Doe", 25)
        
        ' Access properties and methods
        Console.WriteLine("Person: " & person1.GetFullName())
        Console.WriteLine("Age: " & person1.Age)
        
        If person1.IsAdult() Then
            Console.WriteLine(person1.FirstName & " is an adult")
        Else
            Console.WriteLine(person1.FirstName & " is a minor")
        End If
        
        Console.ReadLine()
    End Sub
End Module

Output:

Person: Jane Doe
Age: 25
Jane is an adult

Summary

In this guide, we've covered the basic elements of VB.NET programming:

• Syntax fundamentals including modules, subroutines, and comments
• Variables and data types for storing different kinds of information
• Control structures like If-Then-Else, Select Case, and various loops
• Arrays and collections for managing groups of related data
• Functions and subroutines for organizing and reusing code
• Error handling with Try-Catch blocks
• Object-oriented programming basics with classes and objects

VB.NET combines a readable syntax with the power and flexibility of the .NET platform, making it an excellent choice for building Windows applications, web services, and more.

Additional Resources

To further develop your VB.NET skills:

1. Microsoft Documentation: Visit Microsoft's official VB.NET documentation for in-depth guides and reference materials.

2. Books:

   • "Visual Basic .NET Step by Step" by Microsoft Press
   • "Programming in Visual Basic 2010" by Julia Case Bradley and Anita Millspaugh

3. Online Courses:

   • Microsoft Learn Platform
   • Pluralsight courses on VB.NET
   • Udemy's VB.NET courses for beginners

Practice Exercises

1. Hello User: Create a program that asks for a user's name and their favorite color, then displays a personalized greeting using that information.

2. Number Analyzer: Write a program that asks the user for a number, then determines if it's positive, negative, or zero, and if it's even or odd.

3. Shopping List Manager: Develop an application that lets users add items to a shopping list, view all items, and remove items.

4. Temperature Converter: Create a program that converts temperatures between Celsius and Fahrenheit based on user input.

5. Student Grade Calculator: Build an application that calculates the average grade from a collection of student scores and assigns a letter grade based on the average.