The Hierarchical Object Store in SharePoint 2010

We find, when building MOSS solutions, that we generally have a need for configuration information stores at four different levels:

• Web application level
• Site collection level
• Site level
• List level

There are lots of options when it comes to choosing configuration information stores, but at the web application level SharePoint offers two choices that are quite natural: the section of the web application web.config file and the hierarchical object store.

Of these two options, the hierarchical object store is by far the lesser known of the two. To put it shortly, the hierarchical object store offers a framework that allows third party applications to store configuration information by creating a class that inherits from the SPPersistedObject class in the Microsoft.SharePoint.Administration namespace.

If you look at the site and list level, besides the hierarchical object store, you have another option offered by SharePoint: the property bag. At the site level, it can be accessed via the Properties property of an instance of the SPWeb class. Instances of SPList classes don’t have a property bag associated to it. However, list items do have such a property bag. Therefore, using the property bag of the root folder of a list is a natural alternative if you want to store list level configuration information.

The last option is a SharePoint construct known as the hierarchical object store. There is no functional difference between the hierarchical object storage and a property bag that is scoped at the SPFarm level, so deciding which to choose is largely a matter of preference. Like property bags, hierarchical object storage is a native capability of SharePoint that is available as soon as a SharePoint server farm is built and is available for the entire life of that farm. This means that any application can interact with the hierarchical object storage without needing to know anything else about the environment. Using the hierarchical object storage is bit more complicated as it requires the creation of a custom object which inherits from SPPersistedObject. Nonetheless, the hierarchical object storage is a valid tool and can be useful in your applications.