Using Monster real time posting API and business gateway

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C#

My work is to develop a solution for real time posting jobOffer from our platform to Monster . we found that Monster provides an API for that and a Business Gateway .
we proceed by adding a web reference and I used method from the service , but the object returned is null and I can't consult if the the request is successfully sent or not .
Is there someone who already worked with thie API to help me : here is my code

public class sendFile : System.Web.UI.Page
{
public string call()
{
System.Net.ServicePointManager.ServerCertificateValidationCallback +=
(s, cert, chain, sslPolicyErrors) => true;

//service class
com.monster.schemas.MonsterBusinessGatewayService gateway = new MonsterBusinessGatewayService();


RecruiterReferenceType rec = new RecruiterReferenceType();
CompanyAuthHeader comp = new CompanyAuthHeader();
Security1 security = new Security1();
MonsterHeader monster = new MonsterHeader();
UsernameTokenType1 user = new UsernameTokenType1();

//Job
job.RecruiterReference = rec;
var r = rec.UserName = "xtestxftp";
job.RecruiterReference.UserName = r;
job.jobRefCode = "testJob";
job.JobInformation = info;
info.JobTitle = "software engineer";
info.JobBody = BodyType;
var v = BodyType.Value = "intersting job ppppppppppppppp ";
// posting Stats
PostingStats postS = new PostingStats();
Postingtype.PostingStats = postS;
var nb = postS.Views;
var nbApp = postS.SeekerApps;

//Business Gataway paramaters
gateway.Url = "https://gateway.monster.com:8443/bgwBroker";
gateway.Proxy = proxy;
proxy.Credentials = cre;
gateway.UseDefaultCredentials = true;
gateway.Proxy.Credentials = System.Net.CredentialCache.DefaultCredentials;

gateway.Security = security;
security.UsernameToken = user;
user.Password = pass;

gateway.Security.UsernameToken.Username = "xrtpjobsx01";
gateway.Security.UsernameToken.Password.Value = "rtp987654";


JobsResponse jobresp = new JobsResponse();
jobresp = gateway.UpdateJob(job);
JobResponse[] jobres = new JobResponse[10];
jobresp.JobResponse = jobres;
jobres[1] = jobresponse;
JobCharge[] jobchrg = new JobCharge[10];
jobresponse.JobCharges = jobchrg;
//jobresponse.JobPostingResponse[1].JobViewURL =
jobchrg[1] = jobcharge;
string postId = jobcharge.postingId;
var requestXmlFile = XMLSerializerClass.SerializeSOAPFile(job, "C:/Users/DELL/Desktop/req.xml");
var ResponseXmlFile = XMLSerializerClass.SerializeSOAPFile(jobresp, "C:/Users/DELL/Desktop/resp.xml");

return postId;
}
}