Week 1 – 3 Recap

Useful links/info:

TPITVB.blogspot.com

VB.NET Week 1Outline: Introduction Simple walk through Coding Conventions

Coding ConventionsAll keywords – Start with Capital

Example: Dim As Integer String BooleanIf Then Else ElseIf End If Select Case Case End Select

All variable name – Start with small letterExample: i x y nameOfVariable existingString

total sumOfNumber

VB.NET Week 2Outline: Variables Strings Operators Maths helper functions Application: Create a Calculator for addition

Variables - DeclaringDeclare a variable using the Dim and As

keywords:Dim sumOfNumber As Integer

Name of variable: sumOfNumberType: Integer

(Dim: Short for dimension)

Variables - DeclaringData Type Summary

Boolean True, False

Date 8 bytes to store date and time

Double 8 bytes to store decimals(others: Single, Decimal)

Integer 4 bytes to store whole number(others: Short, Long)

String word or sentence(for just one character: Char)

Single: single-precision decimal (floating point)

Double: double-precision decimal

Java8 primitive types:

byteshortintlongfloatdoublebooleanchar

String – not primitive type

Variables - assigningAssign a value to your variable with the =

sign, which is sometimes called the assignment operator

sumOfNumber = 42 This line of code takes the value 42 and stores

it in the previously declared variable named sumOfNumber

The equals sign is not actually an equals sign. The = sign here means assign a value of.

Variables - assigningDeclaring and Assigning Variables with a

Default Value Dim sumOf Number As Integer = 0Dim nameOfPerson As String = "None"

Arithmetics Operators

+ Addition

- Subtraction

* Multiplication

/ Division

Other Arithmetic Operators^ to the power ofmod remainder after division (Java:%)\ division but return only integer

portion

Short cut:+= x += y same as x = x + y-= x -= y same as x = x - y*= x *= y same as x = x * y/= x /= y same as x = x / y

Do not have these operatorsJava++- -

Comparison OperatorsOperator Examples

= (equals) 5 = 4 (false)

4 = 5 (false)

4 = 4 (true)

<> (not equal to) 5 <> 4 (true)

4 <> 5 (true)

4 <> 4 (false)

Comparison operators

are used to in condition

Eg If (condition) doSomthing

Comparison OperatorsOperator Examples

> (greater than) 5 > 4 (true)

4 > 5 (false)

4 > 4 (false)

< (less than) 5 < 4 (false)

4 < 5 (true)

4 < 4 (false)

Comparison OperatorsOperator Examples

>= (greater than or equal to)

5 >= 4 (true)

4 >= 5 (false)

4 >= 4 (true)

<= (less than or equal to)

5 <= 4 (false)

4 <= 5 (true)

4 <= 4 (true)

Conversion from String to other types

Use CType if you are not sure the name of

the conversion function

Example: to convert to Boolean

CType(variableName, Boolean)

Type Conversion examplesDim inputString As String = TextBox1.Text

Dim x As Integer x = CInt(inputString) ' Convert to Integer.

Dim y As Integer = 8Textbox1.Text = CStr(y) ' Convert to String.

c i n t

c s t r

Maths FunctionsMath.Sqrt(n): Return the square root of n.Math.Abs(n): Return the absolute value of n.Math.Sign(n): Return the sign of n (-1, 0 or +1).

Example: Dim x As Integer

Dim y As Integer = 25

TextBox1.Text = Math.Sqrt(y)

‘ MsgBox("Sq root of 25 is " & CStr(x))

Class vs Local variablesPublic Class Form1

Dim x As Integer = 0 ' Class variables.Dim name As String = ""

Sub Button0_Click …Dim y As Integer = 9 ' Local sub variables.

End Sub

:End Class

x = 5 ' OK or Not?y = 5 ' OK or Not?

x = 5 ' OK or Not?y = 5 ' OK or Not?

VB.NET lesson week Get Input from User If Then Else, Else If Select Case Add condition checking into Simple

Calculator

Get Input from User

Dim name As String

name = InputBox("Enter your name:")

MsgBox("Your name is " & name)

If Then Else, Else IfSyntax

If condition Then

:

End If

Else

:

ElseIf condition2 Then ' Can repeat for

: ' more conditions

Example

If name <> "" Then

MsgBox(name)

End If

Example

If name <> "" Then

MsgBox(name)

Else

MsgBox("Empty")

End If

Example

If name = "" Then

MsgBox("Empty")

ElseIf name = "me" Then

MsgBox("Me")

Else

MsgBox(name)

End If

More than one conditionAnd condition1 And condition2

AndAlso condition1 AndAlso condition2Recommended - Short-circuit And

Eg If i > 0 AndAlso j <> 5 Then

Once i > 0 is false, no need to check j <> 5

More than one conditionOr condition1 Or condition2

OrElse condition1 OrElse condition2Recommended - Short-circuit Or

Eg If i > 0 OrAlso j <> 5 Then

Once i > 0 is true, no need to check j <> 5

Short cut If and AssignmentIIf Immediate If

x = IIf( i > 0, 1, 0)

Same As

If i > 0 Thenx = 1

Elsex = 0

End If

Select CaseSyntax

Select Case variable

Case condition1

:

Case condition2

:

Case Else

:

End Select

Example

Select Case name

Case ""

MsgBox("Empty")

Case "Me"

MsgBox("me")

Case Else

MsgBox(name)

End Select

Select Case ConditionsCase "red", "white", "green" ' A few together .

Case 1 To 10 ' A range using

' keyword To .Case Is > 9 ' A range using

' keyword Is .

Javaif (condition) {

:} else if (condition 2) {

} else {:

}

switch variable {case 1:

:break;

case 2::break;

default::

}

End of lessons