What is VB.NET and IDE?

---

1. Visual Development

VB.NET is a visual programming language, in which applications are created using a graphical user interface (GUI). It supports drag-and-drop tools, event-driven programming, and visual designing.

Key Features:

• GUI-based Development: The application's interface is created using the form designer.

• Event-driven Programming: Code is executed on events like button clicks, mouse movements, keyboard input.

• Real-time Preview: A real-time preview of the designed form can be seen.

• Code and Design: Both coding and visual design can be managed together.

---

2. Variables

Variables are used to store data in programming.

(A) Declaring Variables

In VB.NET, a variable is declared with the Dim keyword.

Dim x As Integer
Dim name As String

(B) Data Types

VB.NET has various types of data types:

• Integer

• Double

• String

• Boolean (True/False)

• Date

(C) Scope and Lifetime of a Variable

• Scope: Where the variable can be used.

  • Local Variable: Is available only in a function or block.

  • Global Variable: Can be used throughout the program.

• Lifetime: How long the variable remains in memory.

---

3. Control Flow Statements

Control Flow Statements are used to control the flow of the program.

(A) Conditional Statements

These are used to run code based on a condition.

1. If...Then...Else

   If age >= 18 Then
       Console.WriteLine("You are eligible to vote.")
   Else
       Console.WriteLine("You are not eligible to vote.")
   End If

2. Select Case

   Dim grade As Char = "A"
   Select Case grade
       Case "A"
           Console.WriteLine("Excellent")
       Case "B"
           Console.WriteLine("Good")
       Case Else
           Console.WriteLine("Invalid Grade")
   End Select
   

(B) Loop Statements

Loops are used to repeat a process multiple times.

1. For Loop

For i As Integer = 1 To 5
    Console.WriteLine(i)
Next

2. While Loop

Dim i As Integer = 1
While i <= 5
    Console.WriteLine(i)
    i += 1
End While

3. Do While Loop

Dim i As Integer = 1
Do While i <= 5
    Console.WriteLine(i)
    i += 1
Loop

---

4. Constants, Arrays, Types of Arrays, Collections

(A) Constants

Constants are variables whose value cannot be changed during the program.

Const Pi As Double = 3.14159

(B) Arrays

Arrays are used to store data of the same type.

• Single-Dimensional Array

Dim numbers(4) As Integer
numbers(0) = 10
numbers(1) = 20

• Multi-Dimensional Array

Dim matrix(2,2) As Integer
matrix(0,0) = 1
matrix(0,1) = 2

(C) Collections

Collections are used for dynamic data storage.

Dim names As New List(Of String)
names.Add("Rahul")
names.Add("Amit")

---

5. Subroutines & Functions

(A) Passing Variable Number of Arguments

Function AddNumbers(ByVal ParamArray numbers() As Integer) As Integer
    Dim sum As Integer = 0
    For Each num In numbers
        sum += num
    Next
    Return sum
End Function

(B) Optional Arguments

Sub Greet(Optional ByVal name As String = "Guest")
    Console.WriteLine("Hello, " & name)
End Sub

(C) Returning Value from Function

Function Square(ByVal num As Integer) As Integer
    Return num * num
End Function

---

6. MsgBox & InputBox

• MsgBox: A dialog box that is used to show a message to the user.

MsgBox("Welcome to VB.NET")

• InputBox: To take input from the user.

Dim userInput As String
userInput = InputBox("Enter your name:")

---

7. Object-Oriented Programming in VB.NET

(A) Class

Class Person
    Public name As String
End Class

(B) Constructor

Class Student
    Public Sub New()
        Console.WriteLine("Student Object Created")
    End Sub
End Class

(C) Inheritance

Class Animal
    Public Sub Speak()
        Console.WriteLine("Animal speaks")
    End Sub
End Class

Class Dog
    Inherits Animal
End Class

(D) Overriding

Class Parent
    Public Overridable Sub Show()
        Console.WriteLine("Parent class method")
    End Sub
End Class

Class Child
    Inherits Parent
    Public Overrides Sub Show()
        Console.WriteLine("Child class method")
    End Sub
End Class

---

8. Working with Forms

(A) Loading, Showing, and Hiding Forms

Dim frm As New Form2()
frm.Show()
Me.Hide()

(B) Controlling One Form Within Another

Dim frm As New Form2()
frm.MdiParent = Me
frm.Show()