Unit 02

In VB.NET, boxing and unboxing are mechanisms used to convert between value types and reference types. These concepts are important in the .NET type system when values need to be treated as objects.

Dim obj As Object
Dim num As Integer = 10
obj = num   ' Boxing

Module Module1
    Sub Main()
        Dim num As Integer = 25
        Dim obj As Object

        obj = num   ' Boxing

        MsgBox("Boxed value = " & obj)
    End Sub
End Module

Dim num As Integer
num = CType(obj, Integer)   ' Unboxing

Module Module1
    Sub Main()
        Dim obj As Object = 50
        Dim num As Integer

        num = CType(obj, Integer)

        MsgBox("Unboxed value = " & num)
    End Sub
End Module

Key Differences Between Boxing and Unboxing

VB.NET provides many built-in Date and Time functions to retrieve, manipulate, and validate date/time values. These functions help programmers perform operations like getting current date, extracting parts of date, and calculating differences.

MsgBox(Now())

MsgBox(Today())

MsgBox(DateString())

MsgBox(TimeOfDay())

MsgBox(TimeString())

MsgBox(Day(#01/22/2026#))

MsgBox(Month(Now()))

MsgBox(Year(Now()))

MsgBox(Hour(Now()))
MsgBox(Minute(Now()))
MsgBox(Second(Now()))

MsgBox(WeekDay(Now()))

MsgBox(WeekDayName(WeekDay(Now())))

MsgBox(MonthName(7, False))

MsgBox(DateAdd(DateInterval.Month, 1, #8/28/2026#))

MsgBox(DateDiff(DateInterval.Day, #05/01/2026#, #05/10/2026#))

MsgBox(DatePart(DateInterval.Day, #05/01/2026#))

MsgBox(IsDate(#01/22/2026#))

VB.NET provides many built-in string functions to perform operations such as searching, comparing, converting, and manipulating strings. These functions help developers process text easily in applications.

Asc(character)

Dim n As Integer
n = Asc("A")
MsgBox(n)

Chr(code)

Dim c As Char
c = Chr(65)
MsgBox(c)

InStr([start], string1, string2, [compare])

Dim pos As Integer
pos = InStr("How Do You Do?", "Do")
MsgBox(pos)

InStrRev(string1, string2)

Dim pos As Integer
pos = InStrRev("Hello World Hello", "Hello")
MsgBox(pos)

StrReverse(string)

Dim s As String
s = StrReverse("Hello")
MsgBox(s)

StrComp(string1, string2, comparemethod)

Dim result As Integer
result = StrComp("ABCD", "abcd", CompareMethod.Text)
MsgBox(result)

StrConv(string, conversion)

Dim s As String
s = StrConv("hello world", VbStrConv.ProperCase)
MsgBox(s)

StrDup(number, character)

Dim s As String
s = StrDup(5, "A")
MsgBox(s)

Filter(array, match, include, compare)

Dim arr() As String = {"This","Is","It"}
Dim res() As String
res = Filter(arr, "Is", True, CompareMethod.Text)
MsgBox(res(0))

MsgBox is a built-in function in VB.NET used to display a message dialog box to the user. It is commonly used to show information, warnings, errors, or to get user responses like Yes/No.

Definition

MsgBox displays a pop-up message box containing text, buttons, and icons, and optionally returns a value indicating which button the user clicked.

Syntax

MsgBox(prompt[, buttons][, title])

Parameters

• promptMessage text to display.
• buttonsType of buttons and icon (optional).
• titleTitle of the message box (optional).

Simple Example

Module Module1
    Sub Main()
        MsgBox("Welcome to VB.NET")
    End Sub
End Module

MsgBox with Title

MsgBox("Welcome", , "My Application")

MsgBox with Buttons (Yes/No)

Dim result As Integer
result = MsgBox("Do you want to exit?", MsgBoxStyle.YesNo, "Confirm")

Common MsgBoxStyle Constants

Example with Icon

MsgBox("File not found", MsgBoxStyle.Critical, "Error")

Return Values of MsgBox