Question

Getting this error when try to add an item to my repositories/context:

Collection has been modified. Possibly the inventory operation is not performed.

What I’m trying to do

Campaign c = Campaignrepository.FindById(id);
if (c.LandingPage == null)
{
    c.LandingPage = new Page() { Campaign = c, CampaignID = c.Campaignid };
    PageRepository.Add(c.LandingPage);
}
if (c.RedeemPage == null)
{
    c.RedeemPage = new RedeemPage() { Campaign = c, CampaignID = c.Campaignid };
    PageRepository.Add(c.RedeemPage);
}

The Repository Add method:

public void Add(Page p)
{
    pages.Add(p);
    context.SaveChanges();
}

Update: still same error.

After applying the suggestions:

public ActionResult Edit(int id)
{
    Campaign c = Campaignrepository.FindById(id);
    Campaign newreferenceC = Campaignrepository.FindById(id);
    if (c.LandingPage == null)
    {
        c.LandingPage = new Page() { Campaign = newreferenceC, CampaignID = newreferenceC.Campaignid };
        PageRepository.Add(c.LandingPage);
    }
    if (c.RedeemPage == null)
    {
        c.RedeemPage = new RedeemPage() { Campaign = newreferenceC, CampaignID = newreferenceC.Campaignid };
        PageRepository.Add(c.RedeemPage);
    }
    return View("Edit", Campaignrepository.FindById(id));
}

Answer 1

Manged to fix it with:

        Page landingPage = new Page(c);
        RedeemPage redeemPage = new RedeemPage(c);
        PageRepository.Add(landingPage);
        PageRepository.Add(redeemPage);
        c.LandingPage = landingPage;
        c.RedeemPage = redeemPage;
        Campaignrepository.Update(c);