Lesson 8 : Select Case Control Structure

In previous lesson, we have learned how to control the program flow using If...Then...ElseIf control structure. In this lesson, you shall examine another way to control the program flow, that is, the Select Case control structure. The Select Case control structure is slightly different from the If....ElseIf control structure .The difference is that the Select Case control structure can handle conditions with multiple outcomes in an easier manner than the If...Then...ElseIf control structure. The syntax of the Select Case control structure is show below:

Select Case expression
Case value1
        Block of one or more VB statements
   Case value2
        Block of one or more VB Statements
  
        .
   Case Else
        Block of one or more VB Statements
End Select

Example 8.1

Dim grade As String
Private Sub Compute_Click( )
grade=txtgrade.Text
Select Case grade
  Case  "A"
       result.Caption="High  Distinction"
  Case "A-"
      result.Caption="Distinction"
  Case "B"
        result.Caption="Credit"
  Case "C"
        result.Caption="Pass"
  Case Else
        result.Caption="Fail"
  End Select
End Sub

Example 8.2

Dim mark As Single

Private Sub Compute_Click()
'Examination Marks
 mark = mrk.Text
 
Select Case mark
 Case Is >= 85
 
     comment.Caption = "Excellence"
Case Is >= 70
 
    comment.Caption = "Good"

Case Is >= 60
   comment.Caption = "Above Average"
Case Is >= 50
comment.Caption = "Average"
Case Else
comment.Caption = "Need to work harder"
End Select
End Sub

Example 8.3

Example 8.2 can be rewritten  as follows:

Dim mark As Single
Private Sub Compute_Click()
'Examination Marks
mark = mrk.Text

Select Case mark
 Case 0 to 49
comment.Caption =" Need to work harder"
Case 50 to 59>/p>
comment.Caption = "Average"
Case 60 to 69
comment.Caption = "Above Average"
Case 70 to 84
comment.Caption = "Good"
Case Else
comment.Caption = "Excellence"
End Select
End Sub

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