Question

Below is my code.

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Main thread starts and sleeps");
        Student stu = new Student();
        ThreadPool.QueueUserWorkItem(stu.Display, 7);
        ThreadPool.QueueUserWorkItem(stu.Display, 6);
        ThreadPool.QueueUserWorkItem(stu.Display, 5);
        Console.WriteLine("Main thread ends");
    }

}

public class Student
{
    public  void Display(object data)
    {
        Console.WriteLine(data);
    }
}

Every time I run the code, i get different results. I do not mean the order in which they are displayed.

Following are my various results

Main thread starts and sleeps  
Main thread ends


Main thread starts and sleeps
Main thread ends
7
5
6


Main thread starts and sleeps
Main thread ends
7

So, why don’t i get all three numbers displayed every time. Please help.

Answer 1

ThreadPool threads are background threads, meaning they are aborted once your main thread ends. Since no one guarantees that your async methods will have a chance to execute before the last statement, you will get different results each time.