Extending the Namespace of a Primary Snap-in

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This section discusses the steps necessary for an extension snap-in to extend the namespace of a primary snap-in. For more information about working with extension snap-ins, see Working with Extension Snap-ins.

A primary snap-in registers the extendable node types it adds to its namespace. An extension snap-in can extend the namespace of a primary snap-in's node type by adding the appropriate registration code and then implementing the IComponentData interface.

When the user selects a scope item in a primary snap-in that is extended by a namespace extension, MMC requests the extension's IComponentData interface and calls IComponentData::Initialize to initialize the extension's IComponentData object (unless it is already initialized). Like a primary snap-in, a namespace extension can add scope items and enumerate the result pane of any items it adds. When the user selects a scope or result item that a namespace extension has added, MMC uses the extension's IComponentData or IComponent implementation to notify the extension of notification messages and to request data objects.

A namespace extension owns any scope or result items that it adds. Therefore, it can extend its own items by adding context menu items, property pages, toolbars, and other features, just like any other snap-in.

Also, any scope or result items added by a namespace extension can also be extended by other extension snap-ins. The namespace extension then behaves like a primary snap-in, so it must register the node type GUIDs of its extendable node types and publish any clipboard formats that other extension snap-ins require for extracting context information.

Be aware that MMC creates one instance of a namespace extension for each primary snap-in instance that it extends. This namespace extension instance extends all nodes of the appropriate node type that appear under that instance of the primary snap-in.

In the following procedure, be aware that {CLSID}, {snapinCLSID}, and {nodetypeGUID} all denote string representations of the specified CLSIDs and GUIDs. The strings must begin with an open brace ({) and end with a close brace (}).

To extend the namespace of a primary snap-in

  1. The CLSID of each snap-in (extension or stand-alone) must be registered under the HKEY_CLASSES_ROOT\CLSID key in the {CLSID} subkey as an in-process server DLL. The snap-in must also register a threading model for the snap-in CLSID. An apartment threading model is recommended.

    For more information about the HKEY_CLASSES_ROOT\CLSID key, see the CLSID Key. For more information and a code example, see Registering and Unregistering a Snap-in.

  2. All snap-ins must be registered under the HKEY_LOCAL_MACHINE\Software\Microsoft\MMC\SnapIns key in the {snapinCLSID} key. Also, if the namespace extension adds scope or result items that can be extended by other extension snap-ins, add the node type GUIDs of the extendable node types under the HKEY_LOCAL_MACHINE\Software\Microsoft\MMC\SnapIns\{snapinCLSID}\NodeTypes key.

    For more information about the SnapIns key, see Registering and Unregistering a Snap-in.

  3. Register the CLSID of the extension snap-in under the HKEY_LOCAL_MACHINE\Software\Microsoft\MMC\NodeTypes\{nodetypeGUID}\Extensions\Namespace subkey, where nodetypeGUID is the GUID of the node type whose namespace is extended. For more information about the NodeTypes key, see Registration Requirements for Extension Snap-ins.

  4. Implement the IComponentData interface as you would for adding scope items to the scope pane of a primary snap-in. For more information and detailed instructions, see Working with the Scope Pane: Implementation Details.

  5. The namespace extension IComponentData::Notify method will receive an MMCN_EXPAND notification message the first time the user selects a primary snap-in's scope item that is extended by the namespace extension. For the namespace extension to recognize that it is being instructed to add its own items under the primary snap-in scope item, you must implement a mechanism to verify that the currently selected scope item belongs to the primary snap-in or the namespace extension.

  6. If any of the scope items added by the namespace extension also have result pane views, you will need to implement the IComponent interface as well. For more information about the view types available, see Using Different Result Pane View Types.

  7. Also implement the IDataObject interface. MMC will request data objects from the extension snap-in when one of the scope or result items it adds is selected by the user.

  8. If the namespace extension extends its own items by adding context menu items, toolbars, menu buttons, or property pages, implement the required interfaces. For more information, see Working with Toolbars and Menu Buttons and Adding Property Pages and Wizard Pages.

Working with Extension Snap-ins