CODEWITHSUNDEEP
.nettask-parallel-library
kumar
kumar

Reputation: 9387

Continuous while loop in side a task

I am learning TPL C# when i call an infinite while loop inside a task it terminates with out any error. am i doing something wrong? below is the sample code.

class Work2
{
    public void DoWork()
    {
        List<string> scenarios = new List<string>();
        scenarios.Add("work");
        scenarios.Add("climb");
        scenarios.Add("walk");
        scenarios.Add("run");

        List<int> id = new List<int>();
        id.Add(1);
        id.Add(2);
        id.Add(3);
        id.Add(4);

        for (int i = 0; i < 2; i++)
        {
            Task.Factory.StartNew(() =>
            {
                workInstance(id[i], scenarios);
            }, TaskCreationOptions.LongRunning);

            Thread.Sleep(500);
        }     
    }

    public void workInstance(int id, List<string> scenario)
    {
        string Guid = System.Guid.NewGuid().ToString();
        for (int i = 0; i < scenario.Count(); i++)
        {
            scenario[i] = scenario[i] + " " + Guid + " " + Thread.CurrentThread.ManagedThreadId;
        }

        while (true)
        {
            for (int i = 0; i < scenario.Count(); i++)
            {
                Console.WriteLine(scenario[i]);
            }
        }
    }        
}

Upvotes: 1

Views: 2127

Answers (2)

svick
svick

Reputation: 244757

The problem is that you're not waiting for the Tasks to complete. A Process ends when all its foreground Threads complete. If you create a Thread manually, by default it's created as a foreground thread, so your application won't end until all the Threads you created do.

But Tasks are (by default) running on background threads (even if you specify LongRunning). This means you application will end even if there are some Tasks still running.

What you should do to fix that is to wait for all the Tasks to finish. Something like:

var tasks = new Task[2];

for (int i = 0; i < 2; i++)
{
    tasks[i] = Task.Factory.StartNew(() =>
    {
        workInstance(id[i], scenarios);
    }, TaskCreationOptions.LongRunning);
}

Task.WaitAll(tasks);

Upvotes: 2

Patrick D&#39;Souza
Patrick D&#39;Souza

Reputation: 3573

It is a infinite loop as you thought, check the following code

static void Main(string[] args)
{
    Work2 w = new Work2();
    w.DoWork();
    Console.ReadKey();
}

Note that I have added, the following code Console.ReadKey();

I now see a scrolling window with the output being printed and its still running on my PC :)

Debug your code and you will see that the threads being called in the workInstance method have 

Thread.CurrentThread.IsBackground=true

When the main thread exits, i.e. your application exits, the .NET Framework will automatically kill any threads whose IsBackground property is set to "True"

For you reference,

"A thread is either a background thread or a foreground thread. Background threads are identical to foreground threads, except that background threads do not prevent a process from terminating. Once all foreground threads belonging to a process have terminated, the common language runtime ends the process."

Upvotes: 1

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