Question

I have a simple multi-threaded program, with the following structure.

public void someFunction()
{

    List<object> objList = new List<object>();
    //objList populated here

    foreach(object o in objList)
    {
        Thread aThread = new Thread (new ParameterizedThreadStart(doSomething));
        aThread.Start(o);
    }
}

static void doSomething(object o)
{
    //Do something with o.
}

This works well, but I’m having issues limiting the number of simultaneous theads running. Say I want to define int maxThreads = 25 for example. The best way I could think of doing it would be something like:

SomeThreadsafeCounter c = new SomeThreadsafeCounter();

foreach(object o in objList)
{
    while (c < 26){ wait; }
    c++;
    Thread aThread = new Thread (new ParameterizedThreadStart(doSomething));
    aThread.Start(o);
    c--;
}

I’m certain this isn’t the correct way to go about it, is there a better way?

Answer 1

You can do this with the Task parallel library included with .net 4.

ParallelOptions options = new ParallelOptions();
options.MaxDegreeOfParallelism = 25;

Parallel.ForEach(objList, options, item => doSomething(item));

Parallel.ForEach has a number of overloads and I am not sure that I have the correct one here.

More info here: http://msdn.microsoft.com/en-us/library/dd537608.aspx