Conf. dr. Cozgarea Adrian

Structuri de control in VB.NET

1. Structura liniara

2. Structura alternativa

3. Structura repetitiva

Structura liniara

Exemplu:

Dim fact as Factura=New Factura()

fact.Numar=101

fact.Data=Now()

fact.Valoare=1000

fact.CotaTVA=0.24

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Structuri alternative

IF

SELECT CASE

TRY

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IFTHENELSE

1. Sintaxa general:

If conditie1 [ Then ]

[instructiuni1]

[ ElseIf conditie2 [ Then ]

[instructiuni2] ]

[ Else

[ instructiuni3] ]

End If

2. Sintaxa restrns:

If conditie Then [ instructiune1 ] [ Else [ instructiune2 ] ]

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Exemplu IF

If CType(txtNota.Text, Integer)

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SELECT CASE ... END SELECT

Select [ Case ] expresie

[ Case listExpresii1

[ Instruciuni ] ]

[ Case listExpresii2

[ Instruciuni 2] ]

[ Case Else

[ InstruciuniN ] ]

End Select

, unde listExpresii1, listExpresii2:- expresie1 To expresie2

- [ Is ] operatorComparare expresie

- expresie

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Exemplu SELECT CASE

Dim tipCont As String = InputBox("Tastati tip cont: ")

Select Case tipCont.ToUpper()

Case "A"

MsgBox("Cont de activ")

Case "P"

MsgBox("Cont de pasiv")

Case "B"

MsgBox("Cont bifunctional")

Case Else

MsgBox(Cont eronat !")

End Select

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Structuri repetitive

While

Do

For

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WHILE ... END WHILE

While conditie

[ Instruciuni1 ]

[ Exit While ]

[ Instruciuni2 ]

End While

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Exemplu While

Dim i As Integer=1

While i

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Do Loop

Condiionare anterioar:

Do { While | Until } conditie

[ instructiuni1 ]

[ Exit Do ]

[ instructiuni2 ]

Loop

Condiionare posterioar:

Do

[ instructiuni1 ]

[ Exit Do ]

[ instructiuni2 ]

Loop { While | Until } conditie

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Exemple DoLoop

Condiionare anterioar

Dim x As Integer=1

Do While x

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ForNext

Sintaxa 1:

For contor [As tipData]=start To final [Step pas]

[ instructiuni1 ]

[ Exit For ]

[ instructiuni2 ]

Next [ contor ]

Sintaxa 2 (pentru parcurgerea unei multimi):

For Each element [ As tipData ] In multime

[ instructiuni1 ]

[ Exit For ]

[ instructiuni2 ]

Next [ element ]

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Exemple ForNext

Dim x as Integer

For x=0 To 2

MsgBox (x)

Next ' aici este incrementat contorul x

MsgBox (x) ' afiseaza 3 (iteraii)

Dim x As Double=0

For i As Integer=0 To 100 Step 2 ' parcurge numerele pare pe interv. [0,100]

x=x+i

Next

MsgBox (x)