public DirectoryWatcher(string folder)
{
Files = new List<string>();
w = new FileSystemWatcher(folder);
w.Changed += (o, a) => { OnChange(a.FullPath); };
w.Deleted += (o, a) => { OnChange(a.FullPath); };
w.Renamed += (o, a) => { OnChange(a.FullPath); };
}