我不知道如何使用循环和计数器

Question

我需要创建一个程序，可以搜索用户想要搜索的字母。用户将在文本框中写下一些东西，当他/她按下搜索时，将出现一个输入框，要求他在输入框上写一封信。然后程序会告诉你这个字母在文本框中出现了多少次。这是我目前所看到的:

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

我不确定你到底想做什么，但如果你把它限制在一个字符，那么像这样的东西应该工作。

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