C# LoopFileSystemWatcher

This is another implementation of FileSystemWatcher as FileSystemWatcher doesn’t work in all cases.

public class LoopFileSystemWatcher
{
    public delegate void LoopFileSystemEventHandler(object source, LoopFileSystemEvent e);
    public event LoopFileSystemEventHandler created;

    readonly List<string> fileCache = new List<string>();

    private readonly string folderPath;
    private readonly string fileFilter;
    private readonly int checkFrequency;

    private bool cancelled = false;

    public LoopFileSystemWatcher(string folderPath, string fileFilter, int checkFrequency)
    {
        this.folderPath = folderPath;
        this.fileFilter = fileFilter;
        this.checkFrequency = checkFrequency;

        DirectoryInfo dir = new DirectoryInfo(folderPath);
        foreach (FileInfo file in dir.GetFiles(fileFilter))
        {
            fileCache.Add(file.Name);
        }
    }

    public void Wait(int waitSeconds)
    {
        Thread t = new Thread(delegate() { WaitThread(waitSeconds,false); });
        t.Start();
    }

    public FileInfo WaitOnce(int waitSeconds)
    {
        return WaitThread(waitSeconds,true);
    }

    private FileInfo WaitThread(int waitSeconds, bool waitOnce)
    {
        FileInfo lastFile=null;
        DirectoryInfo dir = new DirectoryInfo(folderPath);

        DateTime future = DateTime.Now.AddSeconds(waitSeconds);
        while(DateTime.Now.CompareTo(future)<0)
        {
            if(cancelled)
            {
                return null;
            }

            foreach (FileInfo file in dir.GetFiles(fileFilter))
            {
                if(!fileCache.Contains(file.Name))
                {
                    fireLoopFileSystemEvent(file);
                    fileCache.Add(file.Name);
                    lastFile = file;
                    if(waitOnce)
                    {
                        return file;
                    }
                }
            }
            Thread.Sleep(checkFrequency * 1000);
        }
        return lastFile;
    }

    public void Cancel()
    {
        this.cancelled = true;
    }

    private void fireLoopFileSystemEvent(FileInfo file)
    {
        if (created != null)
        {
            created(this, new LoopFileSystemEvent(file));
        }
    }
}

public class LoopFileSystemEvent : EventArgs
{
    private readonly FileInfo file;

    public LoopFileSystemEvent(FileInfo file)
    {
        this.file = file;
    }

    public FileInfo File
    {
        get { return this.file; }
    }
}