C#

// Initialize the reset events to keep track of completed threads
               ManualResetEvent[] resetEvents = new ManualResetEvent[arrFileName.Count];

               // Launch each method in it's own thread
               for (int i = 0; i < arrFileName.Count; i++)
               {
                   resetEvents[i] = new ManualResetEvent(false);
                   ThreadPool.QueueUserWorkItem(new WaitCallback((object index) =>
                   {
                       int actionIndex = (int)index;

                       // Execute the method
                       ThreadExcecute(arrFileName[actionIndex]);

                       // Tell the calling thread that we're done
                       resetEvents[actionIndex].Set();
                   }), i);
               }

               // Wait for all threads to execute
               WaitHandle.WaitAll(resetEvents);