ObjectStateManager error

I have controller post action

public ActionResult Demographics(string submitButton, DemographicsViewModel model)
{
    switch (submitButton)
    {
        case "Home":
            return RedirectToAction("Index");
        case "Next Page":
            using (ProposalRepository proposalRepository = new ProposalRepository())
            {
                model.Proposal.UserID = proposalRepository.GetUserByName(MasterHelper.CurrentUsername).UserID;
                model.Proposal.CustomerID = proposalRepository.GetCustomerByName(model.CustomerName).CustomerID;

                if (model.Proposal.ProposalID != 0)
                {
                    proposalRepository.Update(model.Proposal);
                }
                else
                {
                    proposalRepository.AddProposal(model.Proposal);
                }

                proposalRepository.SaveChanges();
            }

            return RedirectToAction("GRQuestions", model.Proposal);
        default:
            return View();
    }
}

When I try to update

public void Update(Proposal proposal)
{
    mContext.Proposals.ApplyCurrentValues(proposal);
}

throw error: An object with a key that matches the key of the supplied object could not be found in the ObjectStateManager. Verify that the key values of the supplied object mat开发者_如何学Cch the key values of the object to which changes must be applied. I was looking for a solution and I found this:

public ActionResult Demographics(string submitButton, DemographicsViewModel model)
{
    switch (submitButton)
    {
        case "Home":
            return RedirectToAction("Index");
        case "Next Page":
            using (ProposalRepository proposalRepository = new ProposalRepository())
            {
                Proposal proposal = proposalRepository.GetById(model.Proposal.ProposalID);

                model.Proposal.UserID = proposalRepository.GetUserByName(MasterHelper.CurrentUsername).UserID;
                model.Proposal.CustomerID = proposalRepository.GetCustomerByName(model.CustomerName).CustomerID;

                if (model.Proposal.ProposalID != 0)
                {
                    proposalRepository.Update(model.Proposal);
                }
                else
                {
                    proposalRepository.AddProposal(model.Proposal);
                }

                proposalRepository.SaveChanges();
            }

            return RedirectToAction("GRQuestions", model.Proposal);
        default:
            return View();
    }
}

add only one row:

Proposal proposal = proposalRepository.GetById(model.Proposal.ProposalID);

It works well but I think this is a stupid decision and I believe there is a better way and an explanation???

That is how ApplyCurrentValues works. You must load the entity first to use it (= it is used when modifying attached entity). If you don't want to load it first, change yourUpdate method to:

public void Update(Proposal proposal)
{
    mContext.Proposals.Attach(proposal);
    mContext.ObjectStateManager.ChangeObjectState(proposal, EntityState.Modified);
}