Lecture 4_decisions and Conditions_EDITED

7/25/2019 Lecture 4_decisions and Conditions_EDITED

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LECTURE 4


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4- 2Ayatis Notes + Programming In

Visual Basic.NET by Julia CaseBradley & Anita C. Millspaug

Used to make decisions Always indent for readability & debugging

Then must be on same line as f or !lsef !nd f and !lse must a""ear alone on a line Notice that !lsef is # word$ !nd f is 2

words Always !nd with !nd f


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4- %Ayatis Notes + Programming In


Ifcondition' Thenstatements to "erform if condition(true

[ElseIfcondition' Then

statements to "erform if#st condition(false and2nd condition(true)

[Elsestatements to "erform ifboth conditions( false)

EndIf


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*reater Than > ess Than < !,ual To =

Not !,ual To *reater Than or !,ual To >= ess Than or !,ual to


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4- Ayatis Notes + Programming In


Negati.e numbers are always less than"ositi.e numbers

/trings can be com"ared also don0t

forget to enclose the strings in ,uotes'1AN is less than 13N

3! is less than 3!!//

1oan does not e,ual 1AN

Numbers are always less than letters %5567 is less than orsche


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int9redits(9ntt:t9redits;Te:t'Ifint9redits < %2 Then

rad=reshman;9hecked ( TrueElseIfint9redits < 84 Then

rad/o"homore;9hecked ( TrueElseIfint9redits < >8 Then

rad1unior;9hecked ( TrueElserad/enior;9hecked ( True

EndIf


7/244- ?Ayatis Notes + Programming In


Ifbln/uccessful"eration ( TrueThen

; ; ;EndIf

is equivalent to

Ifbln/uccessful"eration Then; ; ;

EndIf


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Ayatis Notes + Programming InVisual Basic.NET by Julia CaseBradley & Anita C. Millspaug

Use ToUpperand ToLowermethods of the/tring class to con.ert strings forcom"arisons

txtGender.Text contains Male

Ift:t*ender;Te:t;ToUpper( BA! Then; ; ;EndIf


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1oin conditions using ogical "erators r either true e.aluates to true

And both true e.aluates to true

Not re.erses the condition$ so that

true will e.aluate false andfalse will e.aluate true


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IfradBale;9hecked ( True And9ntt:tAge;Te:t' < 2# ThenmintBinorBale9ount + ( mintBinorBale9ount

End If

radBale not checked =alset:tAge greater than 2# =alseradBale not checked$ t:tAge less than 2# =alseradBale checked$ t:tAge 2# or greater =alse

radBale checked$ t:tAge less than 2# True


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Ifrad1unior;9hecked ( True Orrad/enior;9hecked ( True ThenmintU""er9lass9ount + ( mintU""er9lass9ount

End If

rad1unior;Calue(True Truerad/enior;Calue(True Truerad1unior;Calue(=alse$ rad/enior;Calue(True Truerad1unior;Calue(True$ rad/enior;Calue(=alse True

rad1unior;Calue(=alse$ rad/enior;Calue(=alse =alse


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Ifrad1unior;9hecked ( True Orrad/enior;9hecked ( TrueAndradBale;9hecked ( True And9ntt:tAge;Te:t' < 2#

Ifrad1unior;9hecked ( True Orrad/enior;9hecked ( True'And (radBale;9hecked ( True And9ntt:tAge;Te:t''< 2#

Then

mintBinorBale9ount + ( mintBinorBale9ountmintU""er9lass9ount + ( mintU""er9lass9ount

End If


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IfintTem" D %2 ThenIfintTem" D @5 Then

lbl9omment;Te:t ( 3otElse

lbl9omment;Te:t(BoderateEndIf

Elselbl9omment;Te:t(=reeEing

End If


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4- #4Ayatis Notes + Programming In


nstead of coding the 9heck9hangede.ents$ use =s to see which are selected

lace the = code in the 9lick e.ent for aFutton$ such as btuG

ri.ate /ub btuHis"layI9lick'

IfchkFold;9hecked(TrueThen

lblBessage;=ontFold(TrueEndIf

!nd /ub


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4- #Ayatis Notes + Programming In



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4-#8


=or longer$ more com"le: messages store themessage te:t in a /tring .ariable and use that

.ariable as an argument of the /how method

MessageBox.Show(Number of Orders: &_mOrderCount & _

ControlChars.NewLine& Total Sales &_!ormat"e#$mal(mde#Total% _

ControlChars.CrLf& _

'erage Sale: & !ormatNumber(mde#'g% _

Coffee Sales Summar)%

"$m strMessageas Str$ng

"$m strTotalOut as Str$ng

"$m str'gOut as Str$ng

strTotalOut * Total Sales & !ormat"e#$mal(mde#Total%

str'gOut * 'erage Sale: & !ormatNumber(mde#'g%

strNumOrder * Number of Orders: & mOrderCount

strMessage* strNumOrder & _

ControlChars.NewLine& _

strTotalOut _

ControlChars.CrLf& _

str'gOut _

MessageBox.Show(strMessage Coffee Sales Summar)%


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4-#?


ControlChars.NewLine

Used to force to next line

J Bessage Fo: 9an ha.e Bulti"le ut"ut inesJ Kra" longer messages to a second line

J nclude 9ontrol9hars to control the line length and "osition of theline break

BessageFo:;/howLNumber of rdersM L & mrder9ount & I

9ontrol9hars;NewLine& ILTota l/ales & =ormatHecimalmdecTotal' I

9ontrol9hars;CrLf& ILA.erage /aleM L & =ormatNumbermdecA.g' I $ L9oOee /ales /ummary'


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4-#@


Use BessageFo:Futtons9onstants to dis"laymore than one button inthe Bessage Fo:

PecallM Constants covered inCh 3: AbortRetryIgnore, OK,

OKCancel, RetryCancel, YesNo,

YesNoCancel)

MessageBoxButtons.YesNo


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4- #>Ayatis Notes + Programming In


Use BessageFo:Futtons 9onstants todis"lay more than one button in theBessage Fo:9onstants co.ered in 9h %M AbortPetrygnore$ G$G9ancel$ Petry9ancel$ QesNo$ QesNo9ancel'

Bessage Fo:0s /how Bethod returns aDialogResl!obRect that can be checkedto see which button the user clicked

Heclare a .ariable that can hold aninstance of the DialogResl!ty"e toca"ture the outcome of the /how Bethod


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Him dgrResl!as HialogPesultHim s!r"sgas /trings!r"sg= #Clear $rren! order%gresdgrResl!="essage'o)*how(s!r"sg+ ,

"essage'o'!!ons)-esNo+ ,

"essage'oI$on).es!ion +#Clear# /

f dgrResl!( HialogPesult;Qes

Then

De$laring anO01e$! 2aria0le for

!he "e!hodRe!rn


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4- 2#Ayatis Notes + Programming In


Using a diOerent signature for the Bessage Fo:/how method to s"ecify a default buttonM

Him dgrPesult As HialogPesultHim strBessage As /tring09onSrm clear of current order

strBessage ( 9lear the current order Sgures

dgrResl!( BessageFo:;/howstrBessage$ 9lear rder$ I

BessageFo:Futtons;QesNo$BessageFo:con;uestion$ I

BessageFo:HefaultFutton;Futton2$ I

BessageFo:"tions;PightAlign'

Add the

BessageFo:HefaultFutton argument

after theBessageFo:cons

argument

Bessage Fo:"tion Argument

f dgrResl!( HialogPesult;Qes Then09ode to clear the order

!nd f


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9hecking to see if .alid .alues wereentered by user in Te:tFo: 33use BessageFo: to notify user if in.alid

9hecking for re,uired data or not blankM f t:tName;Te:t


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4- 2%Ayatis Notes + Programming In


9ode f structure to determine if .alue

falls within a rangeof acce"table .alues Use nested f structure to .alidate

multi"le .alues on a form Use single f for each .alue$ !lse for message

to user$ and e:ecute o$s "e!hodto resetfocus to te:t bo: in ,uestion

rder of fs should match Tabrder of te:tbo:es on form


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LECTURE 4

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Lecture 4_decisions and Conditions_EDITED