Registering and Unregistering a Snap-in

  • Article

Snap-ins are implemented as COM in-process server DLLs and must be registered appropriately in the MMC registry area.

The following list describes all the places in the registry where a snap-in must register itself. 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 (}).

  • The CLSID of the snap-in 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 its CLSID. The snap-in can specify either ThreadingModel = "Apartment" or ThreadingModel = "Both" for the threading model. Be aware that snap-in developers who are unsure of the requirements imposed by specifying ThreadingModel = "Both" should specify an apartment threading model.

    For more information about the HKEY_CLASSES_ROOT\CLSID key, see the CLSID Key topic.

  • The CLSID of the snap-in must also be registered under the HKEY_LOCAL_MACHINE\Software\Microsoft\MMC\SnapIns key. The SnapIns Key has the following form.

    HKEY_LOCAL_MACHINE\Software\Microsoft\MMC\SnapIns\
    {snapinCLSID}
        NameString REG_SZ "SnapinDisplayName"
        About REG_SZ "{SnapinAboutCLSID}"
        StandAlone
        NodeTypes
            {nodetypeGUID}

  • The {snapinCLSID} key specifies the string representation of the snap-in's CLSID. The string must begin with an open brace ({) and end with a close brace (}).

  • The NameString named value specifies the name of the snap-in displayed in the Add/Remove Snap-in dialog box. If this value is not set, the snap-in appears in the Add/Remove Snap-in dialog box with no name.

  • The About named value specifies the string representation of the CLSID of the object that is created using the CoCreateInstance COM function to get an interface pointer to ISnapInAbout. The string must begin with an open brace ({) and end with a close brace (}). The ISnapInAbout object is created when MMC displays the icon and description for the snap-in in the Add/Remove Snap-in dialog box. If your snap-in does not implement ISnapInAbout or if the About value is not set, no description is displayed and a generic folder icon is displayed in the Add/Remove Snap-in dialog box. For more information about implementing the ISnapInAbout interface, see Adding About Information.

  • The presence of the StandAlone key indicates that the snap-in is a stand-alone snap-in. If the snap-in is a stand-alone snap-in, add the StandAlone key. The snap-in can then be added to the namespace as a stand-alone snap-in in the Standalone tab of the Add/Remove Snap-in dialog box. Be aware that a stand-alone snap-in can also be an extension snap-in (that is, it can extend other snap-ins). If the snap-in is also an extension snap-in, it must be registered for the node types it extends. For more information, see Registration Requirements for Extension Snap-ins.

    If the snap-in is an extension snap-in only, do not add the StandAlone key. If the StandAlone key is not present, the snap-in cannot be added in the Standalone tab. An extension snap-in can extend other snap-ins in the Extensions tab. As stated in the previous paragraph, the extension snap-in must be registered as an extension for the node type that it extends in order for it to appear as an available extension for a stand-alone snap-in.

  • The NodeTypes Key contains subkeys that represent the snap-in's own node types. Each node type is represented as a subkey that is the GUID of the node type. All node types (that is, all node types for the snap-in specified by {snapinCLSID}) that can be extended should be added as subkeys in this key. If the snap-in is stand-alone, the node type for the snap-in's static node can also be added if you want other snap-ins to extend the static node.

    MMC uses the subkeys in this key to find the node types for the snap-in and then uses that list of node types to get the extensions for those node types. That set of extension snap-ins is displayed as available extensions for the snap-in in the Extensions tab of the Add/Remove Snap-in dialog box.

  • The {nodetypeGUID} named value specifies the string representation of the GUID of the node type. The string must begin with an open brace ({) and end with a close brace (}).

    In addition, all extension snap-ins for a particular node type must be registered under the HKEY_LOCAL_MACHINE\Software\Microsoft\MMC\NodeTypes\{nodetypeGUID} key. For more information, see Registration Requirements for Extension Snap-ins.

For more information about the registry, see the Registry topic.

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