某個字符的搜索字符串

Question

我正在創建一個要求用戶輸入部件號的Windows Forms表單，例如「XY12345E678」。然後，使用if-語句將程序搜索第7個位置，並根據該位置中的字符做一些代碼。在這種情況下，它將是「E」或「F」。

例如：

 Dim partNumber as String 
     partNumber = textboxPartNumber.Text 
     Dim seventhPosition as String 
     seventhPosition = partNumber.Substring(7, 1) 

     If seventhPosition *is an "E"* 
     ''' Do some code ''' 
     ElseIf seventhPosition *is an "F"* 
     ''' Do some code ''' 
     Else 
     ''' Do some code ''' 

Answer 1

如果你發現自己寫長If...ElseIf... ElseIf...語句，那麼你應該考慮使用Select Case代替，就像這樣：

Dim partNumber As String = textboxPartNumber.Text 

If partNumber.Length >= 7 Then 
    Dim seventhPosition As String = partNumber.Substring(7, 1) 
    Select Case seventhPosition 
     Case "E" 
      ' some code 
     Case "F" 
      ' some code 
     Case Else 
      ' it is not an "E" or "F" 
    End Select 

Else 
    ' the part number is too short 
End If 

您實際上並不需要使用=在案件條款，但如果你想要你可以使用Case Is = "E"等

Answer 2

你可以用這個試試...

  Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click 
      Dim partNumber As String 
      partNumber = textboxPartNumber.Text 
      Dim seventhPosition As String 
      seventhPosition = partNumber.Substring(7, 1) 

      If seventhPosition = "E" Then 
       MsgBox(seventhPosition) 

      ElseIf seventhPosition = "F" Then 
       MsgBox(seventhPosition) 
      Else 
       MsgBox("others") 
      End If 
     End Sub 

Answer 3

  Dim partNumber As String 
      partNumber = textboxPartNumber.Text 

      Dim seventhPosition As String 
      seventhPosition = partNumber.Chars(7) 

      If seventhPosition = "E" OrElse seventhPosition = "F" Then 
       'Do something 
      End If