VB.NET DataGridView下拉框过滤及空值清除问题求助

我之前参考《DataGridView Cascading/Dependent ComboBox Columns》一文，做了一个包含两个ComboBox列的DataGridView项目：其中第二列SOTTOFASE的选项会根据第一列FASE的选择动态过滤，实现了级联效果。但使用过程中发现，用户误选SOTTOFASE后没有便捷的清除方式，于是我针对性做了处理，下面是具体内容：

原级联ComboBox实现代码 #

先贴出我用来实现级联功能的核心代码：

• 第一列ComboBox：FASE
• 第二列ComboBox：SOTTOFASE

Private Sub DataGridView1_EditingControlShowing(sender As Object, e As DataGridViewEditingControlShowingEventArgs) Handles DataGridView1.EditingControlShowing
    Dim grid = DirectCast(sender, DataGridView)
    If (grid.CurrentCell.ColumnIndex = 1) Then 'State column
        Dim combo = DirectCast(e.Control, DataGridViewComboBoxEditingControl)
        If (grid.CurrentRow.Cells(0).Value IsNot DBNull.Value) Then
            Dim dvStates = New DataView(MondoDBDataSet1.Tables("SOTTOFASI"), $"n_fase = '{grid.CurrentRow.Cells(0).Value}'", "n_fase ASC", DataViewRowState.CurrentRows)
            combo.DataSource = dvStates
            combo.ValueMember = "n_sottofase"
            combo.DisplayMember = "sottofase"
        Else
            combo.DataSource = Nothing
        End If
    End If
End Sub

（附一张展示操作流程3个步骤的图片：）

误选清除的解决方案 #

我通过监听DataGridView的KeyUp事件，实现了按下Delete键一键清除SOTTOFASE列选中值的功能，代码如下：

Private Sub DataGridView1_KeyUp(sender As Object, e As KeyEventArgs) Handles DataGridView1.KeyUp
    If GetAsyncKeyState(Keys.Delete) Then
        Dim CellCombo As DataGridViewComboBoxCell
        If DataGridView1.Rows(DataGridView1.CurrentRow.Index).Cells(1).Value <> -1 Then
            CellCombo = DataGridView1.Rows(DataGridView1.CurrentRow.Index).Cells(1)
            CellCombo.Value = DBNull.Value
        End If
    End If
End Sub

内容的提问来源于stack exchange，提问作者Simone