VB.Net Datagridview组合框添加一个处理程序

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我花了一天时间试图弄清楚如何解决我的问题，这与

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this related unanswered question

在第一个组合框中，我的代码工作正常，没问题。当我尝试更改组合框时，会抛出错误Null Reference Exception

这是我的代码：

Private Sub dgvSurveyQuestions_EditingControlShowing(ByVal sender As Object, ByVal e As DataGridViewEditingControlShowingEventArgs) Handles dgvSurveyQuestions.EditingControlShowing

    Dim editingComboBox As ComboBox = TryCast(e.Control, ComboBox)
    If Not editingComboBox Is Nothing Then
        'Add the handle to your IndexChanged Event

        RemoveHandler editingComboBox.SelectedIndexChanged, AddressOf editingComboBox_SelectedIndexChanged
        AddHandler editingComboBox.SelectedIndexChanged, AddressOf editingComboBox_SelectedIndexChanged

    End If

    'Prevent this event from firing twice, as is normally the case.
    'RemoveHandler dgvSurveyQuestions.EditingControlShowing, AddressOf dgvSurveyQuestions_EditingControlShowing

End Sub

Private Sub editingComboBox_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)

    Dim editingComboBox As ComboBox = TryCast(sender, ComboBox)
    If editingComboBox Is Nothing Then Exit Sub

    'Show your Message Boxes
    MessageBox.Show(editingComboBox.SelectedValue.ToString)  ' throws error here

End Sub

我还在处理不同的解决方法，例如在填充datagridview时添加处理程序或者其他什么..我甚至不知道这是否可行，但我需要这样做。
我真的被困在这里，有人可以解释一下，并建议我该怎么办？感谢

Answer 1

只需检查editingComboBox.SelectedValue是否 Nothing 。

DataGridView仅重用一个ComboBox实例，并在用户选择另一个DataSource单元格时在内部重置ComboBox的{​​{1}}。
然后，事件ComboBox加注，SelectedIndexChanged当时将 Nothing 。