This section discusses the Catalog structure and the names of the items in it, not the semantics of these items. Some of these items have already been covered in the previous chapters, and some are covered in subsequent chapters. The COM+ Catalog’s actual structure, from the root down to the component level, is mapped out in Figure 6-2. Each collection has a predefined identifying name, whereas catalog objects’ names are defined by the user. The root of the Catalog gives you access to top-level collections such as the Applications and TransientSubscription collections (see Chapter 9). You can also access less useful collections such as the communication protocols used by DCOM or all of the in-proc servers (COM objects in a DLL) installed on the machine. Another top-level collection shown in Figure 6-2 is the ComputerList collection—a list of all the computers that the Component Services Explorer is configured to manage.

Figure 6-2.  The COM+ Catalog structure, from the root down to the component level

The Applications collection, as the name implies, contains all the COM+ applications installed on the machine. A catalog object in the Applications collection allows you to set the properties of a particular COM+ application. It also gives you access to two other collections: the Roles and the Components collections. As mentioned previously, every folder in the Component Services Explorer corresponds to a catalog collection. Just as every application in the Component Services Explorer has a Roles and Components subfolder, a catalog object representing an application can give you access to these two collections.

The Roles collection contains a catalog object for each role defined in the application. Chapter 7 discusses role-based security at length. Every catalog object in the Roles collection lets you set its properties (such as the role name and description) and give you access to a collection of users associated with that role, called the UsersInRole collection. Every catalog object in the UsersInRole collection represents a user that was added to that role. As you can see in Figure 6-2, the objects in the UsersInRole collection do not have any collections associated with them.

The Components collection contains a catalog object for each component in the application. You can programmatically configure all the properties available on the properties page of a component in the Component Services Explorer. Every component catalog object can give you access to three collections: the InterfacesForComponent collection, the SubscriptionForComponent collection, and the RolesForComponent collection (see Figure 6-3).

Figure 6-3.  Every component catalog object has an elaborate structure under it

The InterfacesForComponent collection contains a catalog object for every interface the component supports. Every interface catalog object gives you access to its properties and to two collections—one is called the RolesForInterface collection, used to iterate over the roles that were granted access for this interface, and the second collection is the MethodsForInterface collection. The MethodsForInterface collection contains a catalog object for each method on that interface. Each method catalog object can give you access to its properties and to the roles associated with that method, in a collection called RolesForMethod .

Going back to the collections accessible from every component catalog object, the RolesForComponent collection lets you access the roles associated with that component, and the SubscriptionsForComponent collection contains a catalog object per a subscription to a COM+ Event (discussed in Chapter 9). Every subscription object is associated with two collections—the PublisherProperties and the SubscriberProperties collection.

The only role objects that have collections of users associated with them are in the Roles collection accessible from every application object (see Figure 6-2). The component, interface, and method level role objects do not have user collections associated with them (see Figure 6-3).

One more bit of COM+ Catalog trivia—every catalog object always has at least three collections associated with it: the RelatedCollectionInfo , PropertyInfo , and ErrorInfo collections. These collections were omitted from Figure 6-2 and Figure 6-3 for the sake of clarity. The RelatedCollectionInfo collection is used for advanced iterations over the Catalog, allowing you to write generic recursive iteration code that discovers at runtime which collections a particular catalog object is associated with. The PropertyInfo collection is used to retrieve information about the properties that a specified collection supports. The ErrorInfo collection can provide extensive error information for dealing with errors in methods that update more than one catalog object at once, so you can find out exactly which object caused the error. This chapter does not discuss these three advanced collections.

When programming against the COM+ Catalog structure, you need not memorize the Catalog intricate structure. You can just follow the intuitive structure of the Component Services Explorer and simply provide the correct collection name, while using Figures 6-2 and 6-3 as reference navigation maps.