Question

I have a problem in Asp.net C#, .net 3.5

I have the code below :

List<object> objectList = new List<object>();

foreach(var item in listItem)
{
  object obj = getData (item);
  objectList.add(obj);
}
Console.Write("Finish all");

Each time getData (item); fires it takes about 1s;

I want all items in ListItem to run at the same time (here is getData(item)) and then execute after foreach finishes the Console.write("Finish all").

How can I do that?
Any idea will be appreciated!

Answer 1

You could use the ThreadPool and ManualResetEvent:

int itemCount = listItem.Length;
List<object> objectList = new List<object>();
ManualResetEvent[] resetEvents = new ManualResetEvent[itemCount];

for (int i = 0; i < itemCount; i++)
{
    var item = listItem[i];

    resetEvents[i] = new ManualResetEvent(false);
    ThreadPool.QueueUserWorkItem(new WaitCallback((object index) =>
    {
        object obj = getData(item);

        lock (objectList)
            objectList.add(obj);

        resetEvents[(int)index].Set();
    }), i);
}

WaitHandle.WaitAll(resetEvents);
Console.Write("Finish all");

The ThreadPool will run the task in background and the current thread will wait for all workers to finish with the ManualResetEvent.