Why popupform is not pop for lookupEdit?

Hi I am working on Winform and Devexpress. I have a customized lookupEdit and I register it as a ribbon repositoryEdit. When I open my form, I can see this lookupEdit, but no popup comes. I开发者_如何学Ct's very strange when my customized control gets initialized, I see visible columns count is 1 because I create one column - but in the onLeave event, I check the column again, I see the visible column is 0. Why does this happen? Here is the code for the onLeave event.

    protected override void OnLeave(EventArgs e)
    {
        if (IsPopupOpen)
        {
            ItemIndex = PopupForm.SelectedIndex;
            _selectfromPopup = true;
        }

        Properties.DisplayMember = Properties.Columns[0].Caption; // Visible Column Count is 0, why?

        base.OnLeave(e);

        if (textChanged)
            OnLeaveWithChangedText(e);

    }

I traced the code and cannot find out the reason why I cannot see my popup and I cannot select value. Please help me find the root cause of this problem! Thanks a lot!