Safe way to start and use a new Thread?

Question

In a previous question I asked how to improve a bit of code. It was said that I should move it to a new thread. I'd never thought about it before so it seems like a great idea to me. So this morning I went ahead and reused a bit of code I already have for processing emails and updated the way I handle image uploads into my site.

So is this a good way to start a new thread and process the images? Is there even a need to lock it like I am?

private static object dummy = new object();

public static void Save(int nProjId, byte[] bData)
{
    var worker = new ThreadStart(() => ProcessImage(nProjId,bData));
    var thread = new Thread(worker);
    thread.Start();
}

private static void ProcessImage(int nProjId, byte[] bData)
{
    lock (dummy)
    {
        try
        {
            byte[] xlargeImage = Thumbs.ResizeImageFile(bData, 700);
            byte[] largeImage = Thumbs.ResizeImageFile(bData, 500);
            //improved based on previous question to use the already reduced image
            byte[] mediumImage = Thumbs.ResizeImageFile(xlargeImage, 200);
            byte[] smallImage = Thumbs.ResizeImageFile(xlargeImage, 100);

            //existing code to actually save the images
            MyGlobals.GetDataAccessComponent().File_Save(
                ConfigurationManager.ConnectionStrings["ImgStore"], 
                nProjId,
                xlargeImage,
                largeImage,
                mediumImage,
                smallImage);
        }
        catch (Exception)
        {
            //ToDo: add error handleing
            { }
            throw;
        }
    }
}

Oh and the images now upload and process nearly instantly (locally) so it's a HUGE help so far. I just want to make sure it's the best way to do it. Oh and I'm using a dual core machine running Server 2008 with 6gb or ram, so I have a little wiggle room to make it faster or use more threads.

Answer 1

I would suggest using a ThreadPool class, specifically because it will re-use a thread for you rather than you creating a new thread each time, which is a little bit more intensive.

Check out the QueueUserWorkItem method.

Also if you are not using a static resource to write to (I am not sure what exactly File_Save does) I dont think there is a need for your lock. However if you are using a static resource then you should lock just the code that is using it.

Answer 2

Is this for any production code? Or just a sample ? If it is not for production code, apart from using ThreadPool, you can use TPL from .NET4.0 . MS recommends using TPL instead of ThreadPool.