Threading concept in C#

Question

I am new to C# and still learning the threading concept. I wrote a program which is as follows

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;

namespace ConsoleApplication17
{
  class Program
  {
    static void Main(string[] args)
    {
        System.Threading.ThreadStart th1 = new System.Threading.ThreadStart(prnt);
        Thread th = new Thread(th1);
        th.Start();
        bool t = th.IsAlive;
        for (int i = 0; i < 10; i++)
        {
            Console.WriteLine(i + "A");
        }
    }

    private static void prnt()
    {
        for (int i = 0; i < 10; i ++)
        {
            Console.WriteLine(i + "B");
        }
    }
  }
}

I am expecting an output like :-

1A
2A
1B
3A
2B...

as I believe that both main thread and newly created thread should be executing simultaneously.

But the output is ordered , first the prnt function is called and then the Main method for loop is executed.

Answer 1

maybe a cicle of 10 is not enough to see the two thread running at same time. use a longer loop or put a Thread.Sleep (100) within cycle iteration. Starting a thread is quite expensive. What it happens, probably, is that you Main loop get executed before thread loop start, due to the time required for a thread to start

Answer 2

I agree with previous answers you need to add Thread.Sleep(some seconds * 1000)

I recommend you read this article about thread https://msdn.microsoft.com/ru-ru/library/system.threading.thread(v=vs.110).aspx

    static void Main(string[] args)
    {
        Thread th = new Thread(prnt);
        th.Start();
        for (int i = 0; i < 10; i++)
        {
            //sleep one second
            Thread.Sleep(1000);
            Console.WriteLine(i + "A");
        }
        //join the basic thread and 'th' thread 
        th.Join();
    }
    private static void prnt()
    {
        for (int i = 0; i < 10; i++)
        {
            //sleep one second
            Thread.Sleep(1000);
            Console.WriteLine(i + "B");
        }
    }

Answer 3

Updated : A process is used to isolate applications and threads run in the context of that process.

This way, it makes easier for the OS to manage different apps, managing crashes and context switching (slots of time provided to each app to be executed by the CPU). The idea behind is simply run threads during a predefined slot of time, when the time permitted for an app to run is over, the CPU switches to other thread to be executed.

Use the Threading class for small asynchronous tasks in your applications.

See how in the following example you can create a new thread using the System.Threading namespace. Notice how t.Join() is called to wait for the new thread to finish.

Note that the Spleep(1) will force to change the context and that's is what makes the difference with you example. Try to change it back to zero and see the results.

using System;
using System.Threading;

namespace Chapter1
{
    public static class Threads1
    {
        public static void ThreadMethod()
        {
            for (int i = 0; i < 10; i++)
            {
                Console.WriteLine("ThreadProc: {0}", i);
                Thread.Sleep(1);
            }
        }
        public static void Main(string[] args)
        {
            Thread t = new Thread(new ThreadStart(ThreadMethod));
            t.Start();
            for (int i = 0; i < 4; i++)
            {
                Console.WriteLine("Main thread: Do some work.");
                Thread.Sleep(1);
            }
            t.Join();

            Console.Read();
        }
    }
}
// OUTPUT:
//Main thread: Do some work.
//ThreadProc: 0
//ThreadProc: 1
//Main thread: Do some work.
//ThreadProc: 2
//Main thread: Do some work.
//ThreadProc: 3
//Main thread: Do some work.
//ThreadProc: 4
//ThreadProc: 5
//ThreadProc: 6
//ThreadProc: 7
//ThreadProc: 8
//ThreadProc: 9