我不知道如何使用循環和計數器

Question

我需要創建一個程序，可以搜索用戶想要搜索的字母。用戶將在TextBox中寫下一些內容，當他/她按下搜索時，輸入框會出現，要求他在輸入框上寫一個字母。程序會告訴你有很多時間該字母出現在文本框中。這是我到目前爲止有：

Public Class Form1 

    Private Sub BtnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnClear.Click 
     TxtboxInput.Clear() 
    End Sub 

    Private Sub BtnQuit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnQuit.Click 
     Me.Close() 
    End Sub 

    Private Sub BtnSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnSearch.Click 
     Dim intStartIndex As Integer 
     Dim intFoundIndex As Integer 
     Dim counter = 0 
     Dim hitcounter = 0 
     Dim blnFlag = True 
     Try 

      InputBox(" Enter Letters", "Input Needed") 
     Catch 
     End Try 
    End Sub 
End Class 

Answer 1

我不知道正是你正在嘗試做的，但如果你將其限制在一個單一的字符，然後這樣的事情應該工作。

Private Sub BtnSearch_Click(sender As System.Object, e As System.EventArgs) Handles BtnSearch.Click 
    Dim counter = 0 
    Try 
     Dim search As String = InputBox(" Enter Letters", "Input Needed") 
     For Each c As Char In TxtboxInput.Text 
      If c.ToString = search Then 
       counter += 1 
      End If 
     Next 
    Catch 
    End Try 
End Sub