Question

I’m trying to use the following code bellow to fire multiple thread to consume an HttpWebRequest.
I do a foreach in all possible requests (each request has different data), but when I pass the request to the method of consumption, it seems that it only receives always the last item in the list.

Could someone help me fix this error ?

int pending = requests.Count;
var finished = new ManualResetEvent(false);
foreach (Request request in requests)
{
  // Required to close over the loop variable correctly.
  Request capture = request; 
  ThreadPool.QueueUserWorkItem(
    (state) =>
    {
      try
      {
        ProcessRequest(capture);
      }
      finally
      {
         if (Interlocked.Decrement(ref pending) == 0) 
         {
           finished.Set();  // Signal completion of all work items.
         }
      }
    }, null);
}
finished.WaitOne(); // 

Answer 1

Why don’t you pass your requests to threads as state object?
Just pass each request as second parameter to the ThreadPool.QueueUserWorkItem. That is a preferred way of passing data to the thread.

foreach (Request request in requests)
{
  ThreadPool.QueueUserWorkItem(
    state =>
    {
      try
      {
        ProcessRequest(state as Request);
      }
      finally
      {
         if (Interlocked.Decrement(ref pending) == 0) 
         {
           finished.Set();  // Signal completion of all work items.
         }
      }
    }, request);
}