使用組合下拉框計算視覺基本中的文字框中的字母的次數

Question

用這個難看的東西看起來好像不太對。我在文本框中有一些文字。然後，我使用組合放置框來選擇可能出現在文本字段中的字母。然後我需要顯示選定字母出現在文本框中的次數。下面列出的是我的代碼，我得到一些錯誤。那我得到最大的錯誤是

「索引和長度必須引用字符串參數名稱中的位置：長」

我認爲它與子功能做。我認爲它必須對文本框中的字符長度進行一些處理。任何幫助得到這個工作正常是非常讚賞，

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

這應該做你問什麼：

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 

你需要導入System.Text.RegularExpressions爲它工作。

讓我知道如果你有這個問題