Monitoring a directory for new file creation witho

Question

I have to create a Windows service which monitors a specified folder for new files and processes it and moves it to other location.

I started with using FileSystemWatcher. My boss doesn't like FileSystemWatcher and wants me to use polling by using a Timer or any other mechanism other than FileSystemWatcher.

How can you monitor directorying without using FileSystemWatcher using .NET framework?

Answer 1

At program startup, use Directory.GetFiles(path) to get the list of files.

Then create a timer, and in its elapsed event call hasNewFiles:

    static List<string> hasNewFiles(string path, List<string> lastKnownFiles)
    {
        List<string> files = Directory.GetFiles(path).ToList();
        List<string> newFiles = new List<string>();

        foreach (string s in files)
        {
            if (!lastKnownFiles.Contains(s))
                newFiles.Add(s);
        }

        return new List<string>();
    }

In the calling code, you'll have new files if:

    List<string> newFiles = hasNewFiles(path, lastKnownFiles);
    if (newFiles.Count > 0)
    {
        processFiles(newFiles);
        lastKnownFiles = newFiles;
    }

edit: if you want a more linqy solution:

    static IEnumerable<string> hasNewFiles(string path, List<string> lastKnownFiles)
    {
        return from f in Directory.GetFiles(path) 
               where !lastKnownFiles.Contains(f) 
               select f;
    }

    List<string> newFiles = hasNewFiles(path, lastKnownFiles); 
    if (newFiles.Count() > 0) 
    { 
        processFiles(newFiles); 
        lastKnownFiles = newFiles; 
    } 

Answer 2

1) Sounds like your boss is an idiot
2) You will have to use functions like Directory.GetFiles, File.GetLastAccessTime, etc and keep it in memory to check if it changed.