FileMonitor - CodeProject

Introduction

This project makes it possible to monitor your directories and/or your files. The control will generate an event whenever a file or subdirectory is created, updated or deleted.

If you want to know how you can use this control in a MFC application, then look at the page: How to use an ATL-control with MFC.

I've written this project in Visual C++ 6.0 with ATL 3.0, because you can't use multithreading in Visual Basic.

Properties

Name Type R/W Description

Start

Boolean

Read/Write

When set to true, the monitor will start watching the directories.

Returns True if the monitor is started. False when it is not started.

Methods

Name	Returns	Parameters	Description
`AddPath`	/	`ByVal sPathName as String`	Adds a directory for monitoring.
`RemovePath`	/	`ByVal sPathName as String`	Removes a directory.

Events

Name	Parameters	Description
`Notify`	`ByVal sPathName As String`, `ByVal nType As Integer`	Notifies the control that a file (`nType` = 1) or a subdirectory (`nType` = 0) is changed, deleted or created in the directory `sPathName`.

Remarks

It's recommended that you first add all the directories you want to monitor before you start monitoring, because when the monitor is running, it will always be stopped and started again when you add a new directory.

The control was tested on Windows NT and Windows 98.

The control is written with Visual C++ 6.0 using ATL 3.0. The control was tested with Visual Basic 6.0

Resources

These are the resources I've used to create this project:

PRB: Firing Event in Second Thread Causes IPF or GPF

Because I use multithreading in this control and it's not possible to fire an event from within a thread, I used the following trick to fire the event.

The control is created as a window. I pass a pointer of the control to the thread function where I can use the window handle of the control to send a message. This message will be handled and will fire the event to the container of the control.

class ATL_NO_VTABLE CWatch : 
    public CWindowImpl<CWatch>, // The control is implemented as a window
    public CComObjectRootEx<CComSingleThreadModel>,
    public CComCoClass<CWatch, &CLSID_Watch>,
    public IConnectionPointContainerImpl<CWatch>,
    public IDispatchImpl<IWatch, &IID_IWatch, &LIBID_FILEMONITOR>,
    public CProxy_IWatchEvents< CWatch >
{
public:
    CWatch()
    {
        m_bStarted = false;
        m_hEvent = NULL;
        m_hThread = NULL;
    }
    deqString m_Paths;
    HANDLE m_hEvent;
    HANDLE m_hThread;
    DWORD m_dwThreadId;
    bool m_bStarted;
    cstring m_sNotify;

DECLARE_WND_CLASS(TEXT("Watch"))
BEGIN_MSG_MAP(CWatch)
    MESSAGE_HANDLER(WM_WATCH_NOTIFY, OnWatchNotify) // The messagehandler
END_MSG_MAP()

    LRESULT OnWatchNotify(UINT uMsg, WPARAM wParam, 
        LPARAM lParam, BOOL &bHandled)    // Fires the Notify event
    {
        Fire_Notify(_bstr_t(m_sNotify.c_str()), wParam);
        return 0;
    }
    ...
};

The thread is created as follows in the Start method:

m_hThread = CreateThread(NULL, 0, ThreadFunc, (LPVOID) this, 0, &m_dwThreadId);

As you can see, I pass the this-pointer to the ThreadFunc.

Updates

11 May 2000 - fixed a bug in the AddPath-method
12 Dec 2000 - The major change is that the thread for monitoring the directories is created only once.
In the past, the thread was recreated when you added or removed a path. Now I use an event to notify the thread. When the thread receives the event, it will automatically refresh the FileNotifications.

Check my website for updates.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here