Question

I have to create mutiple web request to same URL using webclient. I spawn thread using thread pool QueueUserWorkItem. Code below show how I am spawning thread and posting using WebClient. I had to derive web client class to set Expect100Continue and Timeout property.

When I run this code without Thread.Sleep (commented line in spawn thread code), I am getting response time over 1500 millisecond. Please check the logic to calculate response time in PostToURL method. But If I put 1 seconds sleep before spawning another thread, I am getting response time less than 300 milliseconds. I could not find reason why is that so different. Actually I need to bring this response time to 300 millisecond. This is test harness code that I am writing to test a service. Can you point why is different response time?

Here is the code that spawns the thread

foreach (var nameValueCollection in requestCollections)
{
    NameValueCollection collection = nameValueCollection;
    ThreadPool.QueueUserWorkItem(a => { if (collection != null) PostToURL    
    (collection); });
    //Thread.Sleep(TimeSpan.FromSeconds(1));
 }

Here is method that post to a URL

public void PostToURL(NameValueCollection collection)
    {
        DateTime requestStartDate = DateTime.Now;
        DateTime requestEndDate = DateTime.Now;
        string encodedResponse;
        try
        {
            using (var transportType2 = new DerivedWebClient())
            {
                transportType2.Expect100Continue = false;
                transportType2.Timeout = TimeSpan.FromMilliseconds(2000);

                ServicePointManager.ServerCertificateValidationCallback =
                    new RemoteCertificateValidationCallback(delegate { return true; });

                requestStartDate = DateTime.Now;
                var responseArray = transportType2.UploadValues("http://xyz/Post.ashx?AccountName=myaccount",
                                                                "POST", collection);
                requestEndDate = DateTime.Now;
                Console.WriteLine(requestEndDate.Subtract(requestStartDate).TotalMilliseconds);

                encodedResponse = Encoding.ASCII.GetString(responseArray);

                transportType2.Dispose();
            }
        }
        catch (Exception exception)
        {
            requestEndDate = DateTime.Now;
            encodedResponse = exception.ToString();
        }

        //Global variable to record request and response
        responses.Add(new ServiceResponse
        {
            ResponseInMs = (int) requestEndDate.Subtract(requestStartDate).TotalMilliseconds,
            StartTime = requestStartDate,
            EndTime = requestEndDate,
            Response = encodedResponse,
            Request = string.Join(";", collection.Cast<string>()
                        .Select(col => String.Concat(col, "=", collection[col])).ToArray()),
            ApplicationId = collection["ApplicationId"]

        });
    }

UPDATED
Here is code that derive webclient

public class DerivedWebClient: WebClient
{
    public bool Expect100Continue
    {
        get;
        set;
    }

    public TimeSpan Timeout
    {
        get;
        set;
    }

    protected override WebRequest GetWebRequest(Uri address)
    {
        var request = (HttpWebRequest)base.GetWebRequest(address);
        if (request != null)
        {
            request.ServicePoint.Expect100Continue = Expect100Continue;
            request.KeepAlive = false;
            request.Timeout = (int) Timeout.TotalMilliseconds;
        }

        return request;
    }
}

Answer 1

This question may be duplicate to UploadValuesAsync response time. But the code blocks are different I would consider different questions but the problem are same. Answer to the other question also, applies here.