Visual basic net
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Visual Basic.NET. Declaring Variables Dim x As Integer Dim y As Integer = 10 Comments ' comment Assignment Statement var= newvalue Constant Const Pi As Double = 3.14159. Visual Basic.NET Data Types. Visual Basic .NET Runtime Storage Range of Values Data Type Data Type Size

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Visual Basic.NET

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Visual basic net

Visual Basic.NET

  • Declaring Variables

    • Dim x As Integer

    • Dim y As Integer = 10

  • Comments

    • ' comment

  • Assignment Statement

    • var= newvalue

  • Constant

    • Const Pi As Double = 3.14159


Visual basic net data types

Visual Basic.NET Data Types

Visual Basic .NET Runtime Storage Range of Values

Data Type Data Type Size

============================================================

Boolean System.Boolean 4 bytes True or False

Byte System.Byte 1 byte 0 to 255 (unsigned)

Char System.Char 2 bytes 1 Unicode “” character

Date System.DateTime 8 bytes January 1, 0001to December 31,9999

Decimal System.Decimal12 bytes +/-0.0 79,228,162,514,264,337,

593,543,950,335

Double System.Double8 bytes -1.797693134862310.0E308 to -4.94065645841247E-324

Integer System.Int32 4 bytes -2,147,483,648 to 2,147,483,647

Long System.Int64 8 bytes -9,223,372,036,854,775,80

to 9,223,372,036,854,775,807

Object System.Object 4 bytes Any data type Depends on usage.

Short System.Int16 2 bytes -32,768 to 32,7670

Single System.Single 4 bytes -3.402823E38 to 0.0

String System.String 10 bytes 0 to approximately billion Unicode char


Data types

Data Types

  • Option Explicit: forces variable declaration

  • Option Strict: forces variable declaration + will not allow conversions where data loss would occur.

  • Data Type Conversion

    • CType (variable_name, New type)

    • ToString method is available in all data types

  • Members available for data types

    • String (Trim, Length, Substring, Replace,..)

    • Array (Length, GetUpperBound, Clear, Sort,..)

    • DateTime (Now,Today,Year,Day,Hour, Add, Subtract, IsLeapYear, DaysInMonth, …)


Vb net operators

VB.NET Operators

Type Operator Purpose Example

Math + Add 5 + 2 = 7

– Subtract 5 – 2 = 3

* Multiply 5 * 2 = 10

/ Divide 5 / 3 = 2.5

\ Integer Divide 5 \ 2 = 2

^ Exponentiation 5^2 = 25

Mod Remainder 5 mod 2 =1

String + Concatenate “one” + “two” = “onetwo”

& Concatenate “one” & “two” = “onetwo”

Assignment = Assigns the value

of expression to variable x = 5 + 3

Math+=Adds the value x += y


Visual basic net

Type Operator Purpose Example

-= Subtracts the x -= y

*= Multiplies the x *= y

/= Divides the x /= y

\= Integer divides x \= y

&= Concatenates the x &= y

^= Exponentiates x ^= y

Comparison = Is equal to If (x = y)

< Is less than If (x < y)

<= Is less than or If (x <=equal to y)

> Is greater than If (x > y)

>= Is greater than If (x >=or equal to y)

<> Is not equal to If (x <> y)

Like Matches a pattern If (x Like “p??r”)

Is Do object variables refer

to same objectIf (x Is y)

Logical And True if both expressions

are true If (x = 3 AND y=4)

Or True if one or If (x = 3 OR y=4)

both expressions are true

Not True if expression is false If Not (x =5)

Xor True if one expression is If (x = 3 Xor y=4)

true, but not both


Arrays

Arrays

  • Specify upper bound of array, starting at index 0

    Dim Names(9) As String `10 elements 0 to 9

    Dim Num () As Integer = { {1,6} , {7,5} , {5,9} }

    Names(0) = “Ahmed”

    Num (2,1)=4

    ReDim Preserve Names(2)

    For Each e in Num

    print e `Read only elements

    Next


Enumeration

Enumeration

Enum UserType

Admin =3

Guest = 2

User= 9

End Enum

Dim user As UserType = UserType.Guest

Dim user2 As UserType = 9


Branching structures

Branching Structures

If (condition) Then

code

Elseif (condition) then

another code

Else

final code

End if


Branching structures1

Branching Structures

Select Case expresssion

Case 1

code 1

Case 2

code2

Case 3

code3

Case Else

Default code

End Select


Looping

Looping

Do While (condition)

code to repeat

Loop

___________________

Do

code to repeat

Loop until (condition)

  • Exit Do `to get out of a loop


Looping1

Looping

For i = init_value To final_value

Code to repeat

Next

  • Exit for ` to get out of loop


Subroutines and functions

Subroutines and Functions

  • Subroutines

    Sub HelloWorld()

    Response.Write(“Hello World”)

    End Sub

    You call a sub using either of the following statements:

    HelloWorld()

    Call HelloWorld()

  • Functions: can return a value to calling program

    Function SayHello() As String

    Return “Hello World”

    End Function

  • NOTE

    • VB.NET requires parentheses around argument lists

    • The default is to pass parameters by value otherwise use “byref” keyward

    • Overload functions of procedures using the “overloads” keywaord


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