using System;  

using System.IO;  

using System.Net; 

using System.Xml;

using System.Text.RegularExpressions;

​

public class Program

    {

        public static void Main()

        {

            Execute();

        }

        public static void Execute()

        {

            string username = "YOUR USERNAME";

            string password = "YOUR PASSWORD";

            HttpWebRequest request = CreateWebRequest();

            XmlDocument soapEnvelopeXml = new XmlDocument();

            soapEnvelopeXml.LoadXml(

                @"<soapenv:Envelope xmlns:soapenv=""http://schemas.xmlsoap.org/soap/envelope/"" xmlns:urn=""urn:enterprise.soap.sforce.com"">

                    <soapenv:Header>

                        <urn:LoginScopeHeader> 

                            <urn:organizationId>00D1x0000008bXM</urn:organizationId>

                        </urn:LoginScopeHeader> 

                    </soapenv:Header> 

                    <soapenv:Body>

                        <urn:login>

                            <urn:username>"+username+@"</urn:username>

                            <urn:password>"+password+@"</urn:password>

                        </urn:login>

                    </soapenv:Body>

                </soapenv:Envelope>"

            );

​

            using (Stream stream = request.GetRequestStream())

            {

                soapEnvelopeXml.Save(stream);

            }

            using (WebResponse response = request.GetResponse())

            {

                using (StreamReader rd = new StreamReader(response.GetResponseStream()))

                {

                    string soapResult = rd.ReadToEnd();

                    string token = getTagValue("sessionId", soapResult);

                    Console.WriteLine("Token: "+token);

                }

            }

        }

        public static string getTagValue(string tagName, string containing){

            Regex regex = new Regex("<"+tagName+">(.*)</"+tagName+">");

            var v = regex.Match(containing);

            string s = v.Groups[1].ToString();

            return s;

        }

        public static HttpWebRequest CreateWebRequest()

        {

            HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(@"https://cs100.salesforce.com/services/Soap/c/43.0 HTTP/1.1");

            webRequest.Headers.Add(@"SoapAction:login");

            webRequest.ContentType = "text/xml;charset=\"utf-8\"";

            webRequest.Accept = "text/xml";

            webRequest.Method = "POST";

            return webRequest;

        }

    }