Hello,

I'm developing an ASP.NET forms webapplication using C#. I have a method which creates a new Order for a customer. It looks similar to this;

    private string CreateOrder(string userName) {
        // Fetch current order
        Order order = FetchOrder(userName);
        if (order.OrderId == 0) {
            // Has no order yet, create a new one
            order.OrderNumber = Utility.GenerateOrderNumber();
            order.Save();
        }
        return order;
    }

The problem here is, it is possible that 1 customer in two requests (threads) could cause this method to be called twice while another thread is also inside this method. This can cause two orders to be created.

How can I properly lock this method, so it can only be executed by one thread at a time per customer?

I tried;

    Mutex mutex = null;
    private string CreateOrder(string userName) {
        if (mutex == null) {
            mutex = new Mutex(true, userName);
        }
        mutex.WaitOne();
        // Code from above
        mutex.ReleaseMutex();
        mutex = null;
        return order;
    }

This works, but on some occasions it hangs on WaitOne and I don't know why. Is there an error, or should I use another method to lock?

Thanks