SharePoint: The Wicked SPWeb.Properties PropertyBag
*** This article is a must read for any developer reading or writing Web (Site) properties ***
If you haven’t already noticed, there are two different API properties on the SPWeb class – AllProperties (a Hashtable) and Properties (a PropertyBag). Apparently the AllProperties is meant to replace Properties, but Properties was left in place for backwards compatibility. Here’s where things get wicked …
The unconventional PropertyBag data type stores its keys in all lowercase, thus not supporting case-sensitive keys, while the conventional Hashtable does support case-sensitive keys. On top of that, while entries added to Properties get propagated to AllProperties with a lowercase key, entries added to AllProperties do not get propagated to Properties. So this what Microsoft gives us developer peons to work with. This is why consultants like myself stay employed.
If you are working with property entries that only your custom application will be reading and writing from, simply always use AllProperties and you will be good to go. However I often find myself having to work with properties that are read or written by SharePoint internals, and SharePoint itself is very inconsistent in its interaction with Web (Site) properties, probably due to its evolving nature being a rather old product as far as software is concerned.
So the best solution that I have come up with to date is to add your entries to both API properties. This ensures the entry will be present in both collections, and also ensures the key will have the correct case in AllProperties. I have found though in order to add to both, the order of the update API calls is important – you must first update the SPWeb object followed by updating the SPWeb.Properties PropertyBag. Performing the updates in the reverse order prevents an entry with a case-sensitive key from being added to AllProperties, and only the lowercase-keyed entry will be exposed in AllProperties. Now that you are probably thoroughly confused, here is the code:
// Add a property entry web.Properties[key] = value; web.AllProperties[key] = value; web.Update(); web.Properties.Update(); // Remove a property entry web.AllProperties.Remove(key); web.Properties[key] = null; web.Update(); web.Properties.Update();
Take a look, or straight up copy, my SharePoint utility class that abstracts away Web property interactions.