Registers a window that receives notifications from the file system or Shell.

Syntax

ULONG SHChangeNotifyRegister(      
    HWND hwnd,
    int fSources,
    LONG fEvents,
    UINT wMsg,
    int cEntries,
    const SHChangeNotifyEntry *pshcne
);

Parameters

hwnd

A handle to the window that receives the change or notification messages.

fSources

One or more of the following values that indicate the type of events for which to receive notifications.

Note  These flags are not defined in the header file. Implementers must define them themselves or use their numeric values in their place.

SHCNRF_InterruptLevel

0x0001. Interrupt level notifications from the file system.

SHCNRF_ShellLevel

0x0002. Shell-level notifications from the shell.

SHCNRF_RecursiveInterrupt

0x1000. Interrupt events on the whole subtree. This flag must be combined with the SHCNRF_InterruptLevel flag. When using this flag, notifications must also be made recursive by setting the fRecursive member of the corresponding SHChangeNotifyEntry structure referenced by pshcne to TRUE. Use of SHCNRF_RecursiveInterrupt on a single level view—for example, a pointer to an item identifier list (PIDL) that is relative and contains only one SHITEMID—will block event notification at the highest level and thereby prevent a recursive, child update. Thus, an icon dragged into the lowest level of a folder hierarchy may fail to appear in the view as expected.

SHCNRF_NewDelivery

0x8000. Messages received use shared memory. Call SHChangeNotification_Lock to access the actual data. Call SHChangeNotification_Unlock to release the memory when done.

Note  This flag is recomended as it provides a more robust delivery method. All clients should specify this flag.

fEvents

Change notification events for which to receive notification.

wMsg

Message to be posted to the window procedure.

cEntries

Number of entries in the pshcne array.

pshcne

[in] Array of SHChangeNotifyEntry structures that contain the notifications. This array should always be set to one when calling SHChangeNotifyRegister or SHChangeNotifyDeregister will not work properly.

Return Value

Returns a positive integer registration ID. Returns zero if out of memory or in response to invalid parameters.

Remarks

See the Change Notify Watcher Sample in the Microsoft Windows Software Development Kit (SDK) for a full example that demonstrates the use of this function.

When a change notification event is raised, the message indicated by wMsg is delivered to the window specified by the hwnd parameter.

• If SHCNRF_NewDelivery is specified, the wParam and lParam values in the message should be passed to SHChangeNotification_Lock as the hChange and dwProcID parameters respectively.
• If SHCNRF_NewDelivery is not specified, wParam is a pointer to two PIDLIST_ABSOLUTE pointers, and lParam specifies the event. The two PIDLIST_ABSOLUTE pointers can be NULL, depending on the event being sent.

For performance reasons, multiple notifications can be combined into a single notification. For example, if a large number of SHCNE_UPDATEITEM notifications are generated for files in the same folder, they can be joined into a single SHCNE_UPDATEDIR notification.

Function Information

Minimum DLL Version	shell32.dll version 5.0 or later
Custom Implementation	No
Header	shlobj.h
Import library	shell32.lib
Minimum operating systems	Windows 2000