Detect File Read in C#

Question

I\'m using FileSystemWatcher to check when a file is modified or deleted, but I\'m wondering if there is any way to check when a file is read by another application.

Answer 1

The easiest way I can think of to do this would be with a timer (System.Threading.Timer) whose callback checks and stores the last

System.IO.File.GetLastAccessTime(path)

Something like (maybe with a bit more locking...)

public class FileAccessWatcher
{

public Dictionary _trackedFiles = new Dictionary();

private Timer _timer;

public event EventHandler> FileAccessed = delegate { };

public FileAccessWatcher()
{
    _timer = new Timer(OnTimerTick, null, 500, Timeout.Infinite);
}

public void Watch(string path)
{
    _trackedFiles[path] = File.GetLastAccessTime(path);
}

public void OnTimerTick(object state)
{
    foreach (var pair in _trackedFiles.ToList())
    {
        var accessed = File.GetLastAccessTime(pair.Key);
        if (pair.Value != accessed)
        {
            _trackedFiles[pair.Key] = accessed;
            FileAccessed(this, new EventArgs(pair.Key));
        }
    }

    _timer.Change(500, Timeout.Infinite);
}
}