/// <summary>
/// This function initializes the monitor by obtaining the current state and then creating and
/// starting the monitor in a background thread,
/// </summary>
public void EnableMonitoring()
{
if (this.Path.Equals(String.Empty)) return;
initialSnapshot = GetFolderSnapshot();
bckrndWorkerMonitor = new BackgroundWorker();
bckrndWorkerMonitor.WorkerSupportsCancellation = true;
bckrndWorkerMonitor.DoWork += new DoWorkEventHandler(onMonitorEvent);
bckrndWorkerMonitor.RunWorkerAsync();
log.Info("Background file watcher monitor process started.");
}
/// <summary>
/// This function returns a current snapshot of the contents of the folder with
/// a timestamp showing when the snapshot was taken.
/// </summary>
/// <returns>snaphot of folder</returns>
private DirectorySnapshot GetFolderSnapshot()
{
DirectorySnapshot snaphot = null;
if (Directory.Exists(this.Path))
{
snaphot = new DirectorySnapshot(this.Path);
foreach (string file in Directory.GetFiles(this.Path, this.Filter))
snaphot.FileList[file] = File.GetCreationTime(file);
snaphot.tsRefreshed = DateTime.Now;
}
return snaphot;
}
/// <summary>
/// This function compares two DirectorySnapshot objects and returns a list of newly added files
/// </summary>
/// <param name="initialSnapshot"></param>
/// <param name="currentSnapshot"></param>
/// <returns>List of new files</returns>
private List<string> CompareSnaphots(DirectorySnapshot initialSnapshot, DirectorySnapshot currentSnapshot)
{
List<string> newFiles = new List<string>();
if (initialSnapshot == null || currentSnapshot == null)
{
log.WarnFormat("FileSystemWatcherEnhanced cannot compare snapshots if snapshot is null.");
return newFiles;
}
lock (initialSnapshot)
{
lock (currentSnapshot)
{
foreach (string file in currentSnapshot.FileList.Keys)
if (!initialSnapshot.FileList.ContainsKey(file))
newFiles.Add(file);
}
}
return newFiles;
}
private void CheckForNewFiles()
{
//obtain current folder state
currentSnapshot = GetFolderSnapshot();
//compare current and initial states to determine new (i.e. unprocessed) files
//Debug.Assert(initialSnapshot != null);
//Debug.Assert(currentSnapshot != null);
List<string> newFiles = CompareSnaphots(initialSnapshot, currentSnapshot);
if (newFiles.Count > 0)
log.InfoFormat("FileSystemWatcherEnhanced monitor found {0} files in {1}", newFiles.Count, this.Path);
foreach (string file in newFiles)
{
log.WarnFormat("FileSystemWatcher monitor found an unprocessed file. Launching delegate to process {0}", file);
fileReceivedHandler.Invoke(this, new FileSystemEventArgs(WatcherChangeTypes.Created, this.Path, file.Replace(this.Path, "").TrimStart('\\')));
}
/// Reset network connection, if dropped
if (!EnableRaisingEvents)
EnableRaisingEvents = true;
/// Reset the "initialState" after a certain period (typically daily) to help ensure we dont get a memory overflow
if (initialSnapshot.tsRefreshed.AddMinutes(initialStateRefreshIntervalMins) < DateTime.Now)
initialSnapshot = GetFolderSnapshot();
}