How to make a ComboBox of a DataGridViewComboBoxColumn accept user new items?

Using a DataGridViewComboBoxColumn, the goal is to make the ComboBoxes accept user's new items and also the possibility of choosing items that are already present.

I'm aware of using EditingControlShowing event of the DataGridView to change the DropDownStyle of the DataGridViewComboBoxEditingControl at run time to allow this, but I'm wondering if this can be done at a lower level.

What I'm doing now is extending DataGridViewComboBoxColumn, DataGridViewComboBoxCell and DataGridViewComboBoxEditingControl, hoping to change the EditingControl's DropDownStyle in the moment I instantiate it. So far, no luck.

The debugger shows the right assignment is being executed, but nonetheless, the DropDownStyle is popping at the EditingControlShowing (using the event for debugging purposes) as DropBoxList, not DropBox, which is the intent.

Here follow the classes:

Public Class DataGridViewComboBoxColumnALT
    Inherits System.Windows.Forms.DataGridViewComboBoxColumn

    Public Sub New()
        开发者_如何学JAVAMe.CellTemplate = New DataGridViewComboBoxCellALT
    End Sub
End Class

Public Class DataGridViewComboBoxCellALT
    Inherits System.Windows.Forms.DataGridViewComboBoxCell
    Public Overrides ReadOnly Property EditType() As Type
        Get
            Return GetType(DataGridViewComboBoxEditingControlALT)
        End Get
    End Property
End Class

Public Class DataGridViewComboBoxEditingControlALT
    Inherits System.Windows.Forms.DataGridViewComboBoxEditingControl
    Implements System.Windows.Forms.IDataGridViewEditingControl
    Public Sub New()
        MyBase.New()
        Me.DropDownStyle = ComboBoxStyle.DropBox
    End Sub
End Class

You need to set DropDownStyle of DataGridView.EditingControl @ InitializeEditingControl method of Inherted cell class

class DataGridViewComboBoxCellExtended : DataGridViewComboBoxCell
{
    public override void InitializeEditingControl(int rowIndex, object initialFormattedValue, DataGridViewCellStyle dataGridViewCellStyle)
    {
        base.InitializeEditingControl(rowIndex, initialFormattedValue, dataGridViewCellStyle);            
        ((DataGridViewComboBoxEditingControlExtended)DataGridView.EditingControl).DropDownStyle = ComboBoxStyle.DropDown;
    }
    public override Type EditType
    {
        get
        {
            return typeof(DataGridViewComboBoxEditingControlExtended);
        }
    }

I argued with the DataGridViewComboBox for ages. It's awful. I eventually used the old trick of creating a (non-datagridview) ComboBox at runtime and floating it over the grid.