第8課：Select Case 的應用

8.1 Select Case 的應用

如果您的程式裡有很多的條件式語句, 用 If..Then..Else 來控制它的流程可能很麻煩。在這種情形下, 最好是使用 Select Case.......End Select.

它的格式如下 :

Select Case 表達式
Case 數值1
 VB 語句
Case 數值2
 VB 語句
 .
 .
Case Else
 VB 語句
End Select

範例 8.1

在这个例子里，您可以根据考试成绩而决定它的等级。

Dim grade As String
Private Sub Compute_Click( )
 grade=txtgrade.Text
Select Case grade
 Case  "A"
  result.Caption="特優"
 Case "A-"
  result.Caption="優等"
 Case "B"
  result.Caption="中等"
 Case "C"
  result.Caption="及格"
 Case Else 

  result.Caption="不及格"
 End Select
End Sub<

範例 8.2

Dim mark As Single
Private Sub Compute_Click()
 mark = mrk.Text
Select Case mark
 Case Is >= 85
  comment.Caption = "特優"
 Case Is >= 70
  comment.Caption = "優等"
 Case Is >= 60
  comment.Caption = "中等"
 Case Is >= 50
  comment.Caption = "及格"
 Case Else
  comment.Caption = "不及格"
 End Select
End Sub<

範例 8.2 c 可以改寫成:

Dim mark As Single
Private Sub Compute_Click() 

'考試成績
mark = mrk.Text

Select Case mark
 Case 0 to 49
  comment.Caption = "不及格"
 Case 50 to 59
  comment.Caption = "及格"
 Case 60 to 69
  comment.Caption = "中等"
 Case 70 to 84
  comment.Caption = "优等"
 Case Else
  comment.Caption = "特優"
 End Select
End Sub

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