Private Sub DataGridView1_EditingControlShowing(ByVal sender As System.Object, _
  ByVal e As System.Windows.Forms.DataGridViewEditingControlShowingEventArgs) _
  Handles DataGridView1.EditingControlShowing
 
   Dim ctrl As DataGridViewComboBoxEditingControl = _
   TryCast(e.Control,DataGridViewComboBoxEditingControl)
 
   If ctrl IsNot Nothing Then
      ctrl.DropDownStyle = ComboBoxStyle.DropDown
   End If
 
End Sub