Question

I have a while loop in a windows service which runs for some x times and inititate x phone calls after reading them from some file . Now if i want to make a user interface which gives an option to stop the phone calls i.e. break the while loop even before it is completed. How shall i do it ?

Lets suppose i have a function .

DialCalls(x)
{
  for(int i= 0 ; i<x ; i++)
  {
    // Initiate call
  }
}

There can be 2,3 DialCalls functions running at the same time in different threads as i have done threading in the application as well . So basically what is best way to break the loop from a webpage maybe.

Answer 1

Using task cancellation ( new in .net 4):

[Fact]
public void StartAndCancel()
{
    var cancellationTokenSource = new CancellationTokenSource();
    var token = cancellationTokenSource.Token;
    var tasks = Enumerable.Repeat(0, 2)
                          .Select(i => Task.Run(() => Dial(token), token))
                          .ToArray(); // start dialing on two threads
    Thread.Sleep(200); // give the tasks time to start
    cancellationTokenSource.Cancel();
    Assert.Throws<AggregateException>(() => Task.WaitAll(tasks));
    Assert.True(tasks.All(t => t.Status == TaskStatus.Canceled));
}

public void Dial(CancellationToken token)
{
    while (true)
    {
        token.ThrowIfCancellationRequested();
        Console.WriteLine("Called from thread {0}", Thread.CurrentThread.ManagedThreadId);
        Thread.Sleep(50);
    }
}

http://blogs.msdn.com/b/csharpfaq/archive/2010/07/19/parallel-programming-task-cancellation.aspx
The task swallows exceptions so there is some cleanup to to, maybe as IDisposable?
About task exceptions