multithreading - C# Waiting for multiple threads to finish

Question

I have a windows forms app that I am checking all the serial ports to see if a particular device is connected.

This is how I spin off each thread. The below code is already spun off the main gui thread.

foreach (cpsComms.cpsSerial ser in availPorts)
{
    Thread t = new Thread(new ParameterizedThreadStart(lookForValidDev));
    t.Start((object)ser);//start thread and pass it the port
}

I want the next line of code to wait until all the threads have finished. I've tried using a t.join in there, but that just processes them linearly.

Answer 1

List<Thread> threads = new List<Thread>();
foreach (cpsComms.cpsSerial ser in availPorts)
{
    Thread t = new Thread(new ParameterizedThreadStart(lookForValidDev));
    t.Start((object)ser);//start thread and pass it the port
    threads.Add(t);
}
foreach(var thread in threads)
{
    thread.Join();
}

Edit

I was looking back at this, and I like the following better

availPorts.Select(ser =>
      {
          Thread thread = new Thread(lookForValidDev);
          thread.Start(ser);
          return thread;
      }).ToList().ForEach(t => t.Join());