Registers an object and its identifying moniker in the Running Object Table (ROT).

HRESULT Register(

DWORD grfFlags,
//Specifies a weak or a strong reference
IUnknown *punkObject,
//Pointer to the object being registered
IMoniker *pmkObjectName,
//Moniker that identifies the object being registered
DWORD *pdwRegister
//Receives value identifying the registration



[in] Specifies whether the ROT's reference to punkObject is weak or strong. This value must be either zero, indicating a weak reference that does not call IUnknown::AddRef; or ROTFLAGS_REGISTRATIONKEEPSALIVE, indicating a strong reference that calls IUnknown::AddRef and can keep the object running. If a strong reference is registered, a strong reference is released when the object's registration is revoked. Most callers specify zero, indicating a weak reference.


[in] Points to the object that is being registered as running.


[in] Points to the moniker that identifies punkObject.


[out] Receives a 32-bit value that can be used to identify this ROT entry in subsequent calls to IRunningObjectTable::Revoke or IRunningObjectTable::NoteChangeTime. The caller cannot specify NULL for this parameter. If an error occurs, *pdwRegister is set to zero.

Return Values


Indicates that the object was successfully registered.


Indicates that the moniker/object pair was successfully registered, but that another object (possibly the same object) has already been registered with the same moniker.


Indicates one or more invalid arguments.


Indicates failure due to insufficient memory.


This method registers a pointer to an object under a moniker that identifies the object. The moniker is used as the key when the table is searched with IRunningObjectTable::GetObject.

Registering a second object with the same moniker, or re-registering the same object with the same moniker, creates a second entry in the ROT. In this case, IRunningObjectTable::Register returns MK_S_MONIKERALREADYREGISTERED. Each call to IRunningObjectTable::Register must be matched by a call to IRunningObjectTable::Revoke because even duplicate entries have different pdwRegister identifiers. A problem with duplicate registrations is that there is no way to determine which object will be returned if the moniker is specified in a subsequent call to IRunningObjectTable::IsRunning.

Notes to Callers

If you're a moniker provider (that is, you hand out monikers identifying your objects to make them accessible to others), you must call the IRunningObjectTable::Register method to register your objects when they begin running. You must also call this method if you rename your objects while they are loaded.

The most common type of moniker provider is a compound-document link source. This includes server applications that support linking to their documents (or portions of a document) and container applications that support linking to embeddings within their documents. Server applications that do not support linking can also use the ROT to cooperate with container applications that support linking to embeddings.

If you're writing a server application, you should register an object with the ROT when it begins running, typically in your implementation of IOleObject::DoVerb. The object must be registered under its full moniker, which requires getting the moniker of its container document using IOleClientSite::GetMoniker. You should also revoke and re-register the object in your implementation of IOleObject::SetMoniker, which is called if the container document is renamed.

If you're writing a container application that supports linking to embeddings, you should register your document with the ROT when it is loaded. If your document is renamed, you should revoke and re-register it with the ROT and call IOleObject::SetMoniker for any embedded objects in the document to give them an opportunity to re-register themselves.

You must cache the identifier returned in pdwRegister, and use it in a call to IRunningObjectTable::Revoke to revoke the registration when the object is no longer running or when its moniker changes. This revocation is important because there is no way for the system to automatically remove entries from the ROT.

The system's implementation of IRunningObjectTable::Register calls IMoniker::Reduce on the pmkObjectName parameter to ensure that the moniker is fully reduced before registration. If a object is known by more than one fully reduced moniker, then it should be registered under all such monikers.

See Also

IMoniker::Reduce, IOleClientSite::GetMoniker, IOleObject::SetMoniker, IRunningObjectTable::IsRunning, IRunningObjectTable::Revoke

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