I am losing items in a custom collection in a usercontrol I have written.

I have created a usercontrol called DockMaster which holds dock-areas I have
set up on the main form (e.g. top, bottom, left etc.).

Dockmaster has a property called DockPositions which is actually a custom
collection (collection class). The collection class holds individual dockpositions
(another user control).

I can add dockpositions to dockmaster at design time. All seems fine. The
control renders correctly on the form.

When I close the form that holds dockmaster, and then re-open it, my collection
is gone. But the controls still exist in the dockmaster container, i.e.
I can still change the properties of individual dockpositions (by clicking
on them inside dockmaster on the form) - but when I go to the dockpositions
collection (accessed from the default properties form) it is empty.

Anyone have any ideas that may help? I have found it really difficult to
find help on component authoring for DotNet.