filesystemwatcher process files on start

[tig2810]

Hi

I have a problem with filesystemwatcher. My program works fine but there's no event to process existing files in the dir on startup and I'm not sure what is the correct way of doing this? I'm still learning c# so be gentle with me!
thanks

[tlhintoq]

There isn't a built in function for that. What you need to do at the start of your process is raise the filesystemwatcher.created event for each file in the folder.

This will make it "look like" all the pre-existing files were just dropped into the folder.

                    foreach (string ThisFile in Directory.GetFiles(PhotoDirectoryPath,"*.jpg"))
                    {
                        string FilePath = Path.GetDirectoryName(ThisFile);
                        string NameOnly = Path.GetFileName(ThisFile);
                        FileSystemEventArgs FSEAe = new FileSystemEventArgs(WatcherChangeTypes.Created, FilePath, NameOnly);
                        fileSystemWatcher1_Created(this, FSEAe);
                    }

I'l warn you right now that trying to directly process from within your filesystemwater.created method can be risky. Depending on how much proccessing you are doing and how many files already exist in the directory you can quickly create a crash.

What happens if there are 5,000 files in the directory when you hit [Start]? You will create 5,000 instances of the .created method.

I suggest that you use the .created method only for adding the new files to a list to be processed, then process that list periodically. This works for me.

[DonBytes]

Also there's always:

        private FileSystemWatcher fileSystemWatcher;
        private void Form1_Load(object sender, EventArgs e)
        {
            String[] filesPresent = Directory.GetFiles(@"C:\");
            fileSystemWatcher = new FileSystemWatcher(@"C:\");
            fileSystemWatcher.Created += new FileSystemEventHandler(fileSystemWatcher_Created);
            fileSystemWatcher.EnableRaisingEvents = true;
 
            foreach (String filename in filesPresent)
                RealWork(filename);
        }
 
        void fileSystemWatcher_Created(object sender, FileSystemEventArgs e)
        {
            RealWork(e.FullPath);
        }
 
        private void RealWork(String filename)
        {
            MessageBox.Show(filename);
            // ...
        }

[tlhintoq]

Also there's always:

        private FileSystemWatcher fileSystemWatcher;
        private void Form1_Load(object sender, EventArgs e)
        {
            String[] filesPresent = Directory.GetFiles(@"C:\");
            fileSystemWatcher = new FileSystemWatcher(@"C:\");
            fileSystemWatcher.Created += new FileSystemEventHandler(fileSystemWatcher_Created);
            fileSystemWatcher.EnableRaisingEvents = true;
 
            foreach (String filename in filesPresent)
                RealWork(filename);
        }
 
        void fileSystemWatcher_Created(object sender, FileSystemEventArgs e)
        {
            RealWork(e.FullPath);
        }
 
        private void RealWork(String filename)
        {
            MessageBox.Show(filename);
            // ...
        }

DonBytes, In essense your approach and mine are the same give or take a little personal coding style: Get the list of files and raise a Created event for it. But as I mentioned, if you try handling all the work directly as you have here in the RealWork() method when there are 5000 files in the directory you're going to crash. There just isn't enough horsepower to go around to handle all that work in the average or even above-average box. It works fine for a simple coding example, but measures have to be taken for extreme situations, like creating a list of files to process then spawn only as many threads as can your box can afford, or handle them sequentially in a loop or whatever makes sense for the particular program.