if(flow.CheckEngineCapacity >= 2000 || (Convert.ToInt32(totalRows) - numberOfRecords) < 2000)
{
          waitHandle.Set();
          Thread fileProcessor = new Thread(delegate () { flow.ProcessExportEngineFlow(waitHandle); });
          fileProcessor.Start();
 }

public class EngineFlow
{
    private static ConcurrentQueue<WebPages> _concurrentWebPageList = new ConcurrentQueue<WebPages>();

    public bool IncreaseEngineFlow(WebPages page)
    {
        bool sucessfullyadded = false;
        if (_concurrentWebPageList.Count <= 2000)
        {
            _concurrentWebPageList.Enqueue(page);
        }
        else
        {
            return sucessfullyadded;
        }
        return sucessfullyadded;
    }

    public int CheckEngineCapacity { get { return _concurrentWebPageList.Count; } }

    private WebPages DecreaseEngineFlow()
    {
        WebPages page;
        _concurrentWebPageList.TryDequeue(out page);
        return page;
    }

    public void ProcessExportEngineFlow(AutoResetEvent waitHandle)
    {
        if (waitHandle.WaitOne() == false)
        {
            Thread.Sleep(100);
        }
        else
        {
            while (!_concurrentWebPageList.IsEmpty)
            {
                Console.WriteLine(DecreaseEngineFlow().URL);
                Console.WriteLine(CheckEngineCapacity);
                waitHandle.Set();
            }
        }
    }