Question

在这个问题上遇到困难时，似乎无法做到这一点。我在文本框中有一些文字。然后我使用组合下拉框选择可能出现在文本字段中的字母。然后，我需要显示所选字母出现在文本框中的次数。下面列出的是我的代码，我收到了一些错误。我得到的最大错误是

“索引和长度必须指向字符串中的位置。参数名称：长度”

我认为这与子字符串功能有关。我认为它必须对文本框中的字符长度做一些事情。任何有助于使其正常工作的帮助非常感谢，

 Private Sub cboSelectText_SelectedIndexChanged(sender As System.Object, e As System.EventArgs) Handles cboSelectText.SelectedIndexChanged


        'value to find
        Dim strLetterToFind As String

        'String to search
        Dim strStringToSearch As String = txtWordsToScan.Text

        'Current Character
        Dim chrCurrentCharacter As Char

        'Length of text
        Dim intLengthOfText As Integer
        intLengthOfText = strStringToSearch.Length

        'Letter totals
        'Dim intLoopCounter As Integer

        'Count for the display
        Dim intLetterA, intLetterE, intLetterI, intLetterO, intLetterU, intLetterCH, intWords As Integer


        Select Case cboSelectText.SelectedIndex
            Case 1
                strLetterToFind = "A"
            Case 2
                strLetterToFind = "E"
            Case 3
                strLetterToFind = "I"
            Case 4
                strLetterToFind = "O"
            Case 5
                strLetterToFind = "U"
            Case 6
                strLetterToFind = "CH"
            Case 7
                strLetterToFind = " "
            Case Else
                strLetterToFind = String.Empty

        End Select

        For intLoopCounter As Integer = 0 To intLengthOfText
            If chrCurrentCharacter = strStringToSearch.Substring(intLoopCounter, 1).ToUpper Then
                If strLetterToFind = "A" Then
                    intLetterA += 1
                    lblANumberTotal.Text = CStr(intLetterA)
                ElseIf chrCurrentCharacter = "E" Then
                    intLetterE += 1
                    lblENumberTotal.Text = CStr(intLetterE)
                ElseIf chrCurrentCharacter = "I" Then
                    intLetterI += 1
                    lblINumberTotal.Text = CStr(intLetterI)
                ElseIf chrCurrentCharacter = "O" Then
                    intLetterO += 1
                    lblONumberTotal.Text = CStr(intLetterO)
                ElseIf chrCurrentCharacter = "U" Then
                    intLetterU += 1
                    lblUNumberTotal.Text = CStr(intLetterU)
                ElseIf chrCurrentCharacter = "CH" Then
                    intLetterCH += 1
                    lblCHNumberTotal.Text = CStr(intLetterCH)
                ElseIf chrCurrentCharacter = " " Then
                    intWords += 1
                    lblTotalNumberWords.Text = CStr(intWords)
                End If

            End If

        Next

    End Sub

Answer 1

这应该做你要求的：

  Dim strLetterToFind  As String

        strLetterToFind = ComboBox1.SelectedItem


        Try
            lblTotalNumberWords.Text =  Regex.Matches(TextBox1.Text,Regex.Escape(strlettertofind)).Count.ToString)
        Catch ex As Exception
            lblTotalNumberWords.Text = "Please select a option in the combo box"
        End Try

您需要导入System.Text.RegularExpressions才能正常工作。

如果您对此有任何问题，请告诉我

使用组合下拉框计算Visual Basic中文本框中字母的次数

1 个答案: