MVC3 - an entity object cannot be referenced by multiple instances of ientitychangetracker

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C#

MVC

I went through similar questions but it dint solve my purpose. Im using the same code in 2 ways : 1. directly through button press 2. Through scheduled tasks.

By method 1 it works fine but method 2 gives that error. My code :

Service -

public virtual int SendCampaign(Campaign campaign, EmailAccount emailAccount,
        IEnumerable<newslettersubscription> subscriptions)
    {
        var campaignSubscriberTrack = new CampaignNewsletterSubscriberTrack();
        if (campaign == null)
            throw new ArgumentNullException("campaign");

        if (emailAccount == null)
            throw new ArgumentNullException("emailAccount");

        int totalEmailsSent = 0;

        foreach (var subscription in subscriptions)
        {
            var tokens = new List<token>();
            _messageTokenProvider.AddStoreTokens(tokens);
            _messageTokenProvider.AddNewsLetterSubscriptionTokens(tokens, subscription);

            string subject = _tokenizer.Replace(campaign.Subject, tokens, false);
            string body = _tokenizer.Replace(campaign.Body, tokens, true);

            var email = new QueuedEmail()
            {
                Priority = 3,
                From = emailAccount.Email,
                FromName = emailAccount.DisplayName,
                To = subscription.Email,
                Subject = subject,
                Body = body,
                CreatedOnUtc = DateTime.UtcNow,
                EmailAccountId = emailAccount.Id
            };
            _queuedEmailService.InsertQueuedEmail(email);
            totalEmailsSent++;

            campaignSubscriberTrack.CampaignId = campaign.Id;
            campaignSubscriberTrack.NewsletterSubscriberId = subscription.Id;
            campaignSubscriberTrack.Campaign = campaign;
            campaignSubscriberTrack.NewsletterSubscription = subscription;
            campaignSubscriberTrack.IsEmailOpened = 0;
            campaignSubscriberTrack.OpenedOnUtc = null;
            Guid guid;
            string id = tokens.Where(t => t.Key.Equals("TrackImage")).Select(t => t.Value).FirstOrDefault();
            var lastPart = (id.Split('/').Last()).Split('=').Last();
            if (lastPart != null)
            {
                guid = new Guid(lastPart);
                campaignSubscriberTrack.ImageGUID = guid;
            }

            InsertCampaignNewsletterSubscriberTrack(campaignSubscriberTrack);

        }
        campaign.CampaignSchedulingTime = 0;
        UpdateCampaign(campaign); 

        return totalEmailsSent;
    }

Class -

public partial class CampaignNewsletterSubscriberTrack 
    {
        public virtual Campaign Campaign { get; set; }
        public virtual int CampaignId { get; set; }
        public virtual NewsLetterSubscription NewsletterSubscription { get; set; }
        public virtual int NewsletterSubscriberId { get; set; }
        public virtual int IsEmailOpened { get; set; }
        public virtual DateTime? OpenedOnUtc { get; set; }
        public virtual Guid ImageGUID { get; set; }
    }
}

Model -

public class CampaignNewsletterSubscriberTrackModel
{
    public int CampaignId { get; set; }

    public int NewsletterSubscriberId { get; set; }

    public int IsEmailOpened { get; set; }

    public DateTime? OpenedOnUtc { get; set; }

    public Guid ImageGUID { get; set; }
}

And in this function the record gets inserted -

public virtual void InsertCampaignNewsletterSubscriberTrack(CampaignNewsletterSubscriberTrack track)
        {
            if (track == null)
                throw new ArgumentNullException("track");

            _campaignNewsletterSubscriberTrackRepository.Insert(track);
        }

Error occurs at --> InsertCampaignNewsletterSubscriberTrack(campaignSubscriberTrack);

what should I do??? Can anyone tell me where I'm going wrong?