Question

I Have this class to demonstrate my problem:

class Program
{
    static List<FileInfo> _foundFiles;
    static int _numberPadding = 0;
    static Thread newThread;

    static void Main(string[] args)
    {
        _foundFiles = new List<FileInfo>();

        _shouldStop = false;
        newThread = new Thread(new ThreadStart(StartSearch));
        newThread.Start();

        newThread.Join();

        Console.WriteLine("Finished");
        Console.ReadKey();
    }

    static volatile bool _shouldStop;

    static void StartSearch()
    {
        IterateFileSystemNon(new DirectoryInfo(@"D:\OLD Melman\Music Backup\iTunes 28-06-11\Music"));
    }

    static void IterateFileSystemNon(DirectoryInfo folder)
    {
        string pad = CreatePadding();

        Console.WriteLine("{0} Directory: {1}", pad, folder.Name);

        foreach (var dir in folder.GetDirectories())
            IterateFileSystemNon(dir);

        pad = CreatePadding();

        foreach (var file in folder.GetFiles())
        {
            if (file.Extension.Contains("mp3"))
            {
                _foundFiles.Add(file);

                Console.WriteLine("{0} File: {1}", pad, file.Name);
            }
        }

        _numberPadding = _numberPadding - 6;
    }

    static string CreatePadding()
    {
        _numberPadding = _numberPadding + 3;

        var stringRepOfPadding = new StringBuilder(_numberPadding);
        for (int i = 0; i < _numberPadding; i++)
        {
            stringRepOfPadding.Append(" ");
        }
        return stringRepOfPadding.ToString();
    }
}

I have theses questions:

1. This works in a console app, but this doesn’t work in a WindowsFormsApplication, it just goes straight to the Join statement, why is this?
2. If the Join statement as Microsoft puts it “is suppose to block the current thread until the spawned thread has finished”. Surely this defeats the object of multi-threading? In my WindowsFormsApplication, I don’t want to block any thread while this thread is running it’s task.
3. Why do I need the Join. Surely when my Iteration void has completed iterating then the thread should just terminate?!
4. How inside the new thread do I indicate it has finished so that it will close the thread?

Answer 1

1. With Join you will hang UI thread. Use BackgroundWorker component to search files in background thread.
2. Do not start thread and join to it. This is same as doing all work sequentially in one thread, because nothing is executed asynchronously in this case.
3. You don’t need Join (see p2). And using Join in UI thread is always bad idea.
4. You don’t need to indicate that thread is finished to close thread. Thread will exit when your thread delegate will finish execution. See Multithreading: Terminating Threads