Sharepoint 2010: How to persist SPList objects?

I a开发者_JAVA百科m writing a replacement for the sharepoint asset picker dialog with additional features.

There is a requirement to browse media libs which are located in other site collections. So I added a configuration page where you can add the URLs to the media libs to the sharepoint property bag.

In the custom AssetPicker dialog I added the SPList objects created from the configured URLs to a member List called medialibs.

I know that it is very important to dspose the SPWeb and SPSite the SPList object belongs to. I do that in the OnUnload event of the page, but discovered that OnUnload is calld every time on postback. I can't rebuild the medialibs list every time in OnLoad because there is a treeview control on the page which holds references to the SPList objects in medialibs. If I dispose and rebuild them, the objects are new and different. The treeview cannot be rebuilt every time, because it would lose the information which nodes are opened.

How do I persist the contents of the medialibs over postback? How do I ensure the SPList objects in medialibs are properly disposed when the user leaves the page?

Thanks!

I'm not sure why you would require medialibs to be persisted. On the initial load, you would populate the TreeView based on your SPList objects. ViewState then handles persistence of the TreeView across requests. SPSite/SPWeb objects would be disposed of at the population stage (using statements work well). Did I miss something?