BackgroundWorker & Timer, reading only new lines of a log file?

Question

My application writes a log file (currently using log4net). I'd like to setup a timer and a background worker to read the log file and print its content into some control in my form, while it's being written.

I can't use the FileSystemWatcher class because seems broken: sometimes the event "changed" fires, sometimes do not. And it has an extremely low "pooling rate".

So I created a Timer and a FileSystemWatcher. On the "tick" event of the timer, the background worker does its job.

The question is: how to read only the lines that are added since the last check of the worker?

public LogForm()
{
    InitializeComponent();
    logWatcherTimer.Start();
}

private void logWatcherTimer_Tick(object sender, EventArgs e)
{
    FileInfo log = new FileInfo(@"C:\log.txt");
    if(!logWorker.IsBusy) logWorker.RunWorkerAsync(log);
}

private void logWorker_DoWork(object sender, DoWorkEventArgs e)
{
    // Read only new lines since last check.
    FileInfo log = (FileInfo) e.Argument;

   // Here is the main question!
}

EDIT: Code Solution (maybe there is a more elegant way?):

private void logWatherWorker_DoWork(object sender, DoWorkEventArgs e)
{
    // retval
    string newLines = string.Empty;
    FileInfo log = (FileInfo) e.Argument;

    // Just skip if log file hasn't changed
    if (lastLogLength == log.Length) return;

    using (StreamReader stream = new StreamReader(log.FullName))
    {
        // Set the position to the last log size and read
        // all the content added
        stream.BaseStream.Position = lastLogLength;
        newLines = stream.ReadToEnd();
    }

    // Keep track of the previuos log length
    lastLogLength = log.Length;

    // Assign the result back to the worker, to be
    // consumed by the form
    e.Result = newLines;
}

Answer 1

Check and store the file size each time you read the log, then start your text reader (or whatever you're using) at that location the next time you read.