Question

I am trying to get 2 threads running in the background to perform tasks. I have to create the threads sequentially and proceed with the program execution. But the second thread must execute it’s work only when the first finishes. Also, One more clarification. I am looking to have this solution on a WPF application. There is no UI feedback needed. All I need is a status update from the first task. I agree if we do all in one thread it will be fine. But we want to have the second thread which does more things seperately even if the user leaves the screen which created this thread.

Here is the sample:

class Program
{

    static string outValue;
    static bool _isFinished = false;

    static void Main(string[] args)
    {
        ThreadStart thread1 = delegate()
        {
            outValue = AnotherClass.FirstLongRunningTask();
            // I need to set the _isFinished after the long running finishes..
            // I cant wait here because I need to kick start the next thread and move on.
            // 
        };
        new Thread(thread1).Start();

        ThreadStart thread2 = delegate()
        {
            while (!_isFinished)
            {
                Thread.Sleep(1000);
                Console.WriteLine("Inside the while loop...");
            }
            if (!string.IsNullOrEmpty(outValue))
            {
                // This should execute only if the _isFinished is true...
                AnotherClass.SecondTask(outValue);    
            }

        };
        new Thread(thread2).Start();

        for (int i = 0; i < 5000; i++)
        {
            Thread.Sleep(500);
            Console.WriteLine("I have to work on this while thread 1 and thread 2 and doing something ...");    
        }    
        Console.ReadLine();

    }



}


public class AnotherClass
{
    public static string FirstLongRunningTask() 
    {
        Thread.Sleep(6000);
        return "From the first long running task...";
    }

    public static void SecondTask(string fromThread1) 
    {
        Thread.Sleep(1000);
        Console.WriteLine(fromThread1);
    }
}

Where do I set the _isFinished?
I can’t use BackgroundWorker threads. Any help is appreciated.

Answer 1

If a thread can only start when another one finishes, you have a very simple solution: execute the entire code on the first thread.

You can use Task.ContinueWith to queue up more work for the same Task.