IExternalConnection::AddConnection method (objidlbase.h)

Increments the count of an object's strong external connections.


DWORD AddConnection(
  [in] DWORD extconn,
  [in] DWORD reserved


[in] extconn

The type of external connection to the object. The only type of external connection currently supported by this interface is strong, which means that the object must remain alive as long as this external connection exists. Strong external connections are represented by the value EXTCONN_STRONG, which is defined in the enumeration EXTCONN.

[in] reserved

Information about the connection. This parameter is reserved for use by OLE. Its value can be zero, but not necessarily. Therefore, implementations of AddConnection should not contain blocks of code whose execution depends on whether a zero value is returned.

Return value

The method returns the count of connections. This value is intended to be used only for debugging purposes.


An object created by a EXE object server relies on its stub manager to call AddConnection whenever a link client activates and therefore creates an external lock on the object. When the link client breaks the connection, the stub manager calls IExternalConnection::ReleaseConnection to release the lock.

DLL object applications exist in the same process space as their objects, so they do not use RPC (remote procedure calls) and do not have stub managers to keep track of external connections. Therefore, DLL servers that support external links to their objects must implement IExternalConnection so that link clients can directly call the interface to inform them when connections are added or released.

The following is a typical implementation for the AddConnection method.

DWORD MyInterface::AddConnection(DWORD extconn, DWORD dwReserved)
    return extconn & EXTCONN_STRONG ? ++m_cStrong : 0;


Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header objidlbase.h (include ObjIdl.h)

See also