I have a control which behaves similar to the drop-down button on a ComboBox.  When you click the button, I want a CommandBar Popup menu to appear below the control.  Making the popup appear is pretty simple, but I'm having trouble getting it to behave the way I want.

With the button on a ComboBox, the drop-down list appears on the MouseDown event.  If I use the MouseDown event to display a popup below the control, the popup will disappear when the user raises the mouse button (as if the user had clicked an area outside the popup).  As best I can tell, the only way to avoid this is to use the MouseUp event.  The problem with using MouseUp is that the user must fully click on the drop-down button (not just mouse down) in order for the popup menu to appear, and this is not consistent with other windows controls like the ComboBox.

Any ideas how I can display a CommandBar Popup menu from a MouseDown event and not have the popup close when the user releases the mouse button?  It's almost as if I need to direct the CommandBar popup NOT to respond to any mouse up/down information when the mouse is positioned over the drop-down button, but I don't have any idea how to handle this.

Nope... that wasn't it.  'CloseSubMenuOnClick' only prevents the menu from closing when you click on a menu item.  In this case, I'm trying to prevent the popup from closing when the user clicks a designated area outside of the popup (in this case, the drop-down portion of a combobox).

In the last release (9.50), a fix was implemented so that the popup menu ignores the first MouseUp command (which was causing most of my problems).  That was a sufficient work-around for now.  I still can't mimic a drop-down the way I would like, but it's close enough.