Visual Basic解析

Question

好的，所以我正在研究一個程序，該程序分析文本框中的輸入並找到一個定界符（例如逗號，空格或使用Enter鍵按下的行），並在每個定界符之前提取每個單詞並將其發布到列表框中。 我仍然不斷出錯。

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
Dim delimiter As String = ""
Dim oldIndex As Integer = 0
Dim newIndex As Integer = 0
Dim length As Integer = 0
Dim tempString As String = ""
Dim tempWord As String = ""
Dim advanceSize As Integer = 0

If RadioButton1.Checked = True Then
    delimiter = ","
    advanceSize = 1
    tempString = TextBox1.Text
    length = tempString.Length
    Do While oldIndex < length
        newIndex = tempString.IndexOf(delimiter)
        tempWord = Mid(tempString, oldIndex, newIndex)
        tempWord.Trim()
        oldIndex = newIndex + advanceSize
        ListBox1.Items.Add(tempWord)
    Loop
ElseIf RadioButton2.Checked = True Then
    delimiter = vbCrLf
    advanceSize = 2
    tempString = TextBox1.Text
    length = tempString.Length
    Do While oldIndex < length
        newIndex = tempString.IndexOf(delimiter)
        newIndex = tempString.IndexOf(delimiter)
        tempWord = Mid(tempString, oldIndex, newIndex)
        tempWord.Trim()
        oldIndex = newIndex + advanceSize
        ListBox1.Items.Add(tempWord)
    Loop
ElseIf RadioButton3.Checked = True Then
        delimiter = " "
        advanceSize = 1
        tempString = TextBox1.Text
        length = tempString.Length
    Do While oldIndex < length
        newIndex = tempString.IndexOf(delimiter)
        newIndex = tempString.IndexOf(delimiter)
        tempWord = Mid(tempString, oldIndex, newIndex)
        tempWord.Trim()
        oldIndex = newIndex + advanceSize
        ListBox1.Items.Add(tempWord)
    Loop
Else
            Exit Sub

Answer 1

在讀取的第一行中，oldindex的值為零。 Mid函數要求第二個參數的數字大於零，因為與string.substring方法不同，它是基於1的，而不是基於0的。 如果將oldindex初始化為1，該錯誤將得到解決。

順便說一句，mid（和.substring）的第三個參數是長度，而不是結束索引。

Answer 2

我可以建議一個可以實現您的問題目標的替代方法嗎？ 您可以使用String.Split函數。 有點奇怪，要拆分成一個字符串，您需要使用一個字符串數組（數組中只能有一個，這是我們所需要的），您必須指定一個StringSplitOptions值，但是除此之外易於使用：

Private Sub bnSplitData_Click(sender As Object, e As EventArgs) Handles bnSplitData.Click
    Dim txt = tbDataToSplit.Text
    Dim delimiter As String() = Nothing

    ' select case true is an easy way of looking at several options:
    Select Case True
        Case rbCommas.Checked
            delimiter = {","}
        Case rbNewLines.Checked
            delimiter = {vbCrLf}
        Case rbSpaces.Checked
            delimiter = {" "}
        Case Else ' default value
            delimiter = {","}
    End Select

    Dim parts = txt.Split(delimiter, StringSplitOptions.RemoveEmptyEntries)
    ' get rid of the old entries
    ListBox1.Items.Clear()
    ' add the new entries all in one go
    ListBox1.Items.AddRange(parts)

End Sub

請注意，我是如何給控件（ListBox1除外）賦予有意義的名稱的-它使引用正確的控件變得更加容易。