Reading file, and monitor new line

Question

I'm looking to create a console application that will read a file, and monitor every new line since it's being write by another process every .5 seconds.

How can I achieve that, within a Console App using .NET 4.5?

Answer 1

As @Sudhakar mentioned, FileSystemWatcher is useful when you want to be notified when a file updates sporadically, and polling at regular intervals is useful when you want to be constantly processing information from an always-growing file (such as a busy log file).

I'd like to add a note about efficiency. If you are concerned with the efficiency and speed of processing large files (many MB or GB), then you will want to track your position in the file as you read and process updates. For example:

// This does exactly what it looks like.
long position = GetMyLastReadPosition();

using (var file = File.Open(filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
{
    if (position == file.Length)
        return;

    file.Position = position;
    using (var reader = new StreamReader(file))
    {
        string line;
        while ((line = reader.ReadLine()) != null)
        {
            // Do reading.
        }
        position = file.Position; // Store this somewhere too.
    }
}

This should allow you to avoid reprocessing any part of a file that you have already processed.