有没有办法在 For Each 中重新开始

Question

我有一个 For Each 语句，我希望能够从在我的组合框中选择某个选项的开头开始。这可能吗？

For Each cbo As ComboBox In s_combos
        For Each cov As String In s_coverage
            If combo.Name = cbo.Name And combo.SelectedIndex = 0 Then
                If txtNewMoney.Text <> "" And b_isSmoker = False Then
                    CalculateRunningTotal(False, cov, , CKeyValuePair.GetComboBoxSelectedKey(s_applicants(counter), True))
                ElseIf txtNewMoney.Text <> "" And b_isSmoker = True Then
                    CalculateRunningTotal(True, cov, , CKeyValuePair.GetComboBoxSelectedKey(s_applicants(counter), True))
                End If
                counter += 1
                Exit For
            End If
        Next

        If combo.Name = cbo.Name And combo.SelectedIndex = 1 Then
           'If this option is selected, start over in For Each
            counter -= 1
            Dim dec As frmDeclined = New frmDeclined(DirectCast(sender, Control).Name, Me)
            dec.ShowDialog()
        End If
Next

Answer 1

你可以改用一个普通的 for 循环，并将迭代器设置回它的初始值。不过，最好对其进行重组以提高效率，如果选择了该选项，第一次循环有什么意义吗？

Answer 2

从循环内部修改For循环的索引通常被认为是不礼貌的。

一种社会可接受的方法是使用While循环，并在循环中递增或重置自变量。

如果您肯定想使用For...Each循环中，您可以在其外部放置一个While循环以进行迭代以有效地重置For......Each循环。在我能想到的几乎所有情况下，这都是不必要的复杂，我通常不推荐它。

Answer 3

您可以创建一个标签并转到它：

GoHere:
For Each cbo As ComboBox In s_combos
        For Each cov As String In s_coverage
            If combo.Name = cbo.Name And combo.SelectedIndex = 0 Then
                If txtNewMoney.Text <> "" And b_isSmoker = False Then
                    CalculateRunningTotal(False, cov, , CKeyValuePair.GetComboBoxSelectedKey(s_applicants(counter), True))
                ElseIf txtNewMoney.Text <> "" And b_isSmoker = True Then
                    CalculateRunningTotal(True, cov, , CKeyValuePair.GetComboBoxSelectedKey(s_applicants(counter), True))
                End If
                counter += 1
                Exit For
            End If
        Next

        If combo.Name = cbo.Name And combo.SelectedIndex = 1 Then
           'If this option is selected, start over in For Each
            counter -= 1
            Dim dec As frmDeclined = New frmDeclined(DirectCast(sender, Control).Name, Me)
            dec.ShowDialog()
            Goto GoHere
        End If
Next