How to avoid the closing of a custom combo box popup window in a custom datagrid?

Question

I was trying to block the closing of a custom combo box popup window in my custom DataGrid. The popup window comes by pressing F4 or ALT+DOWN keys which is getting closed if I press the down arrow for the first time after showing the first value in the combo box as selected. Next time onwards, if I press the F4 key and down arrow, I can move to any item in the popup window and select the item using keyboard and in that case, the popup window is not getting closed till I press the ENTER key or selection using the Mouse. Is there any specific reason for this behaviour or something is missing in my code part? Expecting your help.


I'm using Dot Net 1.1 and onkeypress, onkeydown, ProcessCmdKey methods are there in the myGridComboBox class.

Protected Overrides Sub OnKeyPress(ByVal e As System.Windows.Forms.KeyPressEventArgs)
End Sub

Protected Overrides Sub OnKeyDown(ByVal e As System.Windows.Forms.KeyEventArgs)
End Sub

Protected Overrides Function ProcessCmdKey(ByRef msg As System.Windows.Forms.Message, ByVal keyData As System.Windows.Forms.Keys) As Boolean
End Function