Wait until all threads finished their work in ThreadPool

Question

i have this code:

var list = new List<int>();
for(int i=0;i<10;i++) list.Add(i); 
for(int i=0;i<10;i++)
{
     ThreadPool.QueueUserWorkItem(
         new WaitCallback(x => {
             Console.WriteLine(x);  
         }), list[i]);
} 

And i want to know when all threadpools threads finished their work. How i can to do that?

Answer 1

You'll need to track this yourself.

One option for this is to use a counter and a reset event:

int toProcess = 10;
using(ManualResetEvent resetEvent = new ManualResetEvent(false))
{
    var list = new List<int>();
    for(int i=0;i<10;i++) list.Add(i); 
    for(int i=0;i<10;i++)
    {
        ThreadPool.QueueUserWorkItem(
           new WaitCallback(x => {
              Console.WriteLine(x);  
              // Safely decrement the counter
              if (Interlocked.Decrement(ref toProcess)==0)
                 resetEvent.Set();

           }),list[i]);
    } 

    resetEvent.WaitOne();
}
// When the code reaches here, the 10 threads will be done
Console.WriteLine("Done");