Multi threading, Thread still runs without waiting for other thread

Question

i am developing a program which lets you pick multiple xml files and sends it to a webserver.

Each xml file data sent would be running on a thread so the data sending runs in parallel. The problem i have is that when i enter the first file it responds early without even entering the next couple of files.

I dont know how to make all the threads wait until i type start to send all of them at once on individual threads.I tried a implementation below but it responds too early after i type the first file.

Heres my code:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Xml;

namespace XMLSender
{
    class Program
    {
        private static string serverUrl;

        static void Main(string[] args)
        {
            Console.WriteLine("Please enter the URL to send the XML File");
            serverUrl = Console.ReadLine();
            List<Thread> threads = new List<Thread>();

            string fileName = "";
            do
            {
                Console.WriteLine("Please enter the XML File you Wish to send");
                fileName = Console.ReadLine();
                Thread t = new Thread(new ParameterizedThreadStart(send));               
                threads.Add(t);
            }
            while (fileName != "start"); //Ends if user enters an empty line
            foreach (Thread t in threads)
            {
                t.Start();
            }
            foreach (Thread t in threads)
            {
                t.Join();
            }

        }
        static private void send(object data)
        {
            try
            {
                //ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(serverUrl);
                byte[] bytes;

                //Load XML data from document 
                XmlDocument doc = new XmlDocument();
                doc.Load((string)data);
                string xmlcontents = doc.InnerXml;

                //Send XML data to Webserver
                bytes = Encoding.ASCII.GetBytes(xmlcontents);
                request.ContentType = "text/xml; encoding='utf-8'";
                request.ContentLength = bytes.Length;
                request.Method = "POST";
                Stream requestStream = request.GetRequestStream();
                requestStream.Write(bytes, 0, bytes.Length);
                requestStream.Close();

                // Get response from Webserver
                HttpWebResponse response;
                response = (HttpWebResponse)request.GetResponse();
                Stream responseStream = response.GetResponseStream();
                string responseStr = new StreamReader(responseStream).ReadToEnd();
                Console.Write(responseStr + Environment.NewLine);

            }
            catch (Exception e)
            {
                Console.WriteLine("An Error Occured" + Environment.NewLine + e);
                Console.ReadLine();
            }
        }
    }
}

Answer 1

If you want to start all threads at once, in your do-while loop, dont start the threads yet. (Dont call t.Start())

Instead, save the file names in a list in the meantime and then, after the while loop, place another foreach loop, which then starts all the threads:

string fileName = "";
List<string> names = new List<string>();
do
{
    Console.WriteLine("Please enter the XML File you Wish to send");
    fileName = Console.ReadLine();
    if(fileName != "start") 
    {
        Thread t = new Thread(new ParameterizedThreadStart(send));               
        threads.Add(t);
        names.Add(fileName);
    }
}
while (fileName != "start"); 

foreach (Thread t in threads)
{
    t.Start(names[0]);
    names.RemoveAt(0);
}

Edit: I added a check to be sure that you don't add another thread when you enter start, as the loop will still finish even if the loop condition isn't true anymore.
Without the check a new thread would be added add the end with startas the Parameter.

Answer 2

First, create a ManulResetEvent. This event can make threads wait till a certain event happens. The ManulResetEvent is then triggered when all threads are allowes to continue. Like this:

class Program
{
    private static readonly ManualResetEvent _wait = new ManualResetEvent(false);
    ...

In your thread code, let all threads wait:

static private void send(object data)
{
    _wait.WaitOne();
    ...

In your Main-method trigger the event after entering all files:

...
while (fileName != ""); //Ends if user enters an empty line
_wait.Set()
foreach (Thread t in threads)
    ...

Answer 3

A second solution could be initializing the thread without starting them, but WITH the filename-parameter:

...
filename = Console.ReadLine();
Thread t = new Thread(() => send(filename));
threads.Add(t);
...

And outside your loop, you start all the threads:

foreach (Thread t in threads)
{
    t.Start();
}