EF4 update navigation property An entity object cannot be referenced by multiple instances of IEntityChangeTracker - entity-framework-4

Question

I am trying to implement a let's say "change my account email address" fonctionality.
I want to keep backup of all user emails in (R_EmailAddressHistory table).
Here are some of my project's code.
public bool ChangeEmailAddress(string username, string newEmailAddress, string callbackUrl)
{
DateTime currentUtcTime = DateTime.UtcNow;
R_User currentUser = UserRepo.GetSingle(whereCondition: w=>w.Username == username);
currentUser.UpdateDate = currentUtcTime;
if (currentUser.HasPendingNewEmail)
{
R_EmailAddressHistory currentPendingRequest = EmailHistoRepo.GetSingle(whereCondition: w => w.StatusID == (int)Reno.Common.Enums.RecordStatus.Pending && w.R_User.GId == currentUser.GId);
currentPendingRequest.NewEmail = newEmailAddress;
currentPendingRequest.UpdateDate = currentUtcTime;
EmailHistoRepo.Update(currentPendingRequest);
}
else
{
currentUser.HasPendingNewEmail = true;
R_EmailAddressHistory newEmail = new R_EmailAddressHistory();
newEmail.UserId = currentUser.GId;
newEmail.R_User = currentUser;
newEmail.NewEmail = newEmailAddress;
newEmail.InsertDate = currentUtcTime;
newEmail.StatusID = (int) Reno.Common.Enums.RecordStatus.Pending;
currentUser.R_EmailAddressHistory.Add(newEmail);
}
IdentityResult idtResult = UserRepo.Update(currentUser);
if(idtResult == IdentityResult.Succeeded)
{
//Send notification to current email address for validation before proceeding change email process
bool sendResult = Communication.EmailService.SendChangeEmailValidation(username,currentUser.Email, newEmailAddress, callbackUrl);
return sendResult;
}
else
{
return false;
}
}
The previous method is use to change an email address. Each of my tables (R_User and EmailAddressHistory ) has Repository (UserRepo and EmailHistoRepo). The implement the same IRepositoryBase class, here is the Update methode
public IdentityResult Update(T entity)
{
try
{
if (_currentContext.DbContext.Entry(entity).State == EntityState.Detached)
{
_currentContext.DbContext.Set<T>().Attach(entity);
}
_currentContext.DbContext.Entry(entity).State = EntityState.Modified;
return IdentityResult.Succeeded;
}
catch
{
return IdentityResult.Failed;
}
}
When a user has already a non validate new email address, when he request to change his current email address, I show him the pending new email address and he can change it, in this case I whant to update my historical table instead of creating a new one, cause only one pending new email address is allow. In such a case, my code failed in the line EmailHistoRepo.Update(currentPendingRequest) throwing the error : An entity object cannot be referenced by multiple instances of IEntityChangeTracker.
Can anyone help me?
Thanks
EDIT
I am using MVC(4) with a unitOfWork. My UOW is initialized in a the Controller the first time the DB is queried and the Commit is done in the global.asax file in Appalication_EndRequest (see below).
protected void Application_EndRequest(Object sender, EventArgs e)
{
CommitChanges();
}
private void CommitChanges()
{
Reno.BLL.Services.Singleton.UnitOfWork unitOfWork = Reno.BLL.Services.Singleton.UnitOfWork.GetCurrentInstance(false);
if (unitOfWork != null)
{
unitOfWork.Commit();
unitOfWork.Dispose();
}
}

Answer 1

Your currentUser is modified before updating the emailaddress. Save the changes to currentUser first.
Something like this:
R_User currentUser = UserRepo.GetSingle(whereCondition: w=>w.Username == username);
currentUser.UpdateDate = currentUtcTime;
bool pendingNewEmail = currentUser.HasPendingNewEmail;
UserRepo.Update(currentUser);
if (pendingNewEmail)
{
R_EmailAddressHistory currentPendingRequest = EmailHistoRepo.GetSingle(whereCondition: w => w.StatusID == (int)Reno.Common.Enums.RecordStatus.Pending && w.R_User.GId == currentUser.GId);
currentPendingRequest.NewEmail = newEmailAddress;
currentPendingRequest.UpdateDate = currentUtcTime;
EmailHistoRepo.Update(currentPendingRequest);
}
else

Answer 2

I finally found the answer. The problem was that when I first get the user in line
R_User currentUser = UserRepo.GetSingle(whereCondition: w=>w.Username == username);
The currentUser variable hold a refrence of all of its R_EmailAddressHistory.
And then after, I queried the DB (2nd time) to get the pending email change request (or type R_EmailAddressHistory) to modify its new email and its update date, in line
R_EmailAddressHistory currentPendingRequest = EmailHistoRepo.GetSingle(whereCondition: w => w.StatusID == (int)Reno.Common.Enums.RecordStatus.Pending && w.R_User.GId == currentUser.GId);
currentPendingRequest.NewEmail = newEmailAddress;
currentPendingRequest.UpdateDate = currentUtcTime;
But te last code updates only currentPendingRequest while another reference of the same object which is in currentUser.R_EmailAddressHistory is not update and was already tracked by the context. Therefore, by doing an update on the new instance (EmailHistoRepo.Update(currentPendingRequest)), the code failed: the same object if referenced in 2 places.
So, the solution was (the only thing I modified):
R_User currentUser = UserRepo.GetSingle(whereCondition: w=>w.Username == username);
currentUser.UpdateDate = currentUtcTime;
if (currentUser.HasPendingNewEmail)
{
R_EmailAddressHistory currentPendingRequest = currentUser.R_EmailAddressHistory.Where(h => h.StatusID == (int)Reno.Common.Enums.RecordStatus.Pending).First(); // EmailHistoRepo.GetSingle(whereCondition: w => w.StatusID == (int)Reno.Common.Enums.RecordStatus.Pending && w.R_User.GId == currentUser.GId);
currentPendingRequest.NewEmail = newEmailAddress;
currentPendingRequest.UpdateDate = currentUtcTime;
}
I decided to modify the instance in currentUser variable.