GoodThread.cs

using System.Threading.Tasks;

static void SleepThenPrintSquare(int n) {
    Thread.Sleep(2000);
    Console.WriteLine("{0}", n * n);
}

static void Main() {
    var tasks = new List<Task>(5);

    for (int i = 1; i <= 5; i++) {
        int tmp = i;
        tasks.Add(Task.Factory.StartNew(() => SleepThenPrintSquare(tmp)));
    }

    // Wait for all tasks to finish
    foreach (var t in tasks)
        t.Wait();
}