1. Start off by creating two methods in the Demo class called ParallelInvoke() and PerformSomeTask() that take an integer of seconds to sleep as the parameter:

        public class Demo 
        { 
          public void ParallelInvoke() 
          {         

          } 

          private void PerformSomeTask(int sleepSeconds) 
          {         

          } 
        }

2. Add the following code to the ParallelInvoke() method. This code will call Paralell.Invoke to run the PerformSomeTask() method:

        WriteLine($"Parallel.Invoke started at 
          {DateTime.Now.Second} seconds"); 
        Parallel.Invoke( 
          () => PerformSomeTask(3), 
          () => PerformSomeTask(5), 
          () => PerformSomeTask(2) 
        ); 

        WriteLine($"Parallel.Invoke completed at 
          {DateTime.Now.Second} seconds");

3. In the PerformSomeTask() method, make the thread sleep for the amount of seconds passed to the method as the parameter (converting the seconds to milliseconds by multiplying it by 1000):

        int threadID = Thread.CurrentThread.ManagedThreadId; 
        WriteLine($"Sleep thread {threadID} for 
          {sleepSeconds}  seconds"); 
        Thread.Sleep(sleepSeconds * 1000); 
        WriteLine($"Thread {threadID} resumed");

4. When you've added all the code, your Demo class should look like this:

        public class Demo 
        { 
          public void ParallelInvoke() 
          { 
            WriteLine($"Parallel.Invoke started at 
                      {DateTime.Now.Second} seconds"); 
            Parallel.Invoke( 
              () => PerformSomeTask(3), 
              () => PerformSomeTask(5), 
              () => PerformSomeTask(2) 
            ); 

            WriteLine($"Parallel.Invoke completed at {DateTime.Now.Second} 
                      seconds");            
          } 

          private void PerformSomeTask(int sleepSeconds) 
          {         
            int threadID = Thread.CurrentThread.ManagedThreadId; 
            WriteLine($"Sleep thread {threadID} for {sleepSeconds} 
                      seconds"); 
            Thread.Sleep(sleepSeconds * 1000); 
            WriteLine($"Thread {threadID} resumed"); 
          } 
        }

5. In the console application, instantiate a new instance of the Demo class and call the ParallelInvoke() method:

        Demo oRecipe = new Demo(); 
        oRecipe.ParallelInvoke(); 
        Console.ReadLine();

6. Run the console application and look at the output produced in the console window: