Estructura de Selección en Visual Basic

COMP 215

Definición

• La estructura de selección la utilizamos cuando necesitamos programar el computador para que, dependiendo del cumplimiento o no de ciertas condiciones dentro del programa, se ejecuten o no instrucciones.

If Blocks

• If condition Then action1Else action2End If

Flowchart general

Is the condition true?

Execute action2 Execute action1

TN

ElseIf clauses

If condition1 Then action1ElseIf condition2 Then action2ElseIf condition3 Then action3Else action4End If

Ejemplo programación ElseIf ElseIf Public Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim gpa As Double Dim honors As String gpa = CDbl(TextBox1.Text) If gpa >= 3.9 Then honors = "summa cum laude..." ElseIf gpa >= 3.6 Then honors = "magna cum laude..." ElseIf gpa >= 3.3 Then honors = "cum laude..." ElseIf gpa >= 2.0 Then honors = "........." Else honors = "You don't graduated..." End If TextBox2.Text = gpa & " " & honors End SubEnd Class

Select Case Block

Select Case selector Case valueList 1 action1 Case valueList 2 action2 Case Else action of last resortEnd Select

Ejemplo programación Select CaseSelect CasePublic Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim gpa As Double Dim honors As String gpa = CDbl(TextBox1.Text) Select Case gpa Case Is >= 3.9 honors = "summa cum laude..." Case Is >=3.6 honors = "magna cum laude..." Case Is >= 3.3 honors = "cum laude..." Case Is >=2.0 honors = "........." Case Else honors = "You don't graduated..." End Select TextBox2.Text = gpa & " " & honors End SubEnd Class