如何获取字符串中的前一个字符

Question

我正在创建一个函数，它允许我在 for 循环期间获取字符串中的前一个字符。

Private Sub TSButton_Click(sender As Object, e As EventArgs) Handles TSButton.Click
    For Each ch As Char In HTextDisplay.Text
        MsgBox("the previous characters here")
        'carry out function here
    Next
End Sub

所以如果HTextDisplay.Text 是“ABCDEFG”，那么消息框将显示“A”然后是“B”然后是“C”.....

另一方面，如果我可以检查for循环函数中字符后面是否有字符，我可能会更好

Answer 1

dim previousChar as char = ""
For Each ch as Char in HTextDisplay.Text
    msgbox ch & " - previous character = " & previousChar
    'other processing
    previouschar = ch
Next