Visual Basic 解析

Question

好的，所以我正在开发一个程序，该程序解析文本框中的输入并找到分隔符，例如逗号、space，或使用回车键按下的行，并在每个分隔符和将其张贴在列表框中。不过我总是收到错误。

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

在读取的第一行中，oldindex 的值为零。 Mid 函数的第二个参数需要一个大于零的数字，因为与 string.substring 方法不同，它是从一开始而不是从零开始。如果将 oldindex 初始化为 1，该错误将得到解决。

顺便说一句，mid（和.substring）的第三个参数是长度，而不是结束索引。

Answer 2

我可以建议一个替代方案来实现您的问题的目标吗？您可以使用 String.Split 函数。这有点麻烦，因为要拆分一个字符串，您需要使用一个字符串数组（数组中可以只有一个，这就是我们所需要的）并且您必须指定一个 StringSplitOptions 值，但除此之外它是易于使用：

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

请注意我是如何为控件（ListBox1 除外）赋予有意义的名称的 - 这样更容易引用正确的名称。

Visual Basic 解析

Visual Basic Parsing

visual-studio-2010

parsing

textbox

listbox