EF: how to modify existing entry in DB in N-layered application

Question

Im not EF specialist propably, but I have an issue with it:).

Im doing n-layered business application, so I have Service code and Repository code in my app. In my service code, it read existing User entity, I do update of some properties and it calls Repositiry' method Edit. And there error appears:

Attaching an entity of type 'MobileWallet.Common.Repository.MwbeUserData' failed because another entity of the same type already has the same primary key value. This can happen when using the 'Attach' method or setting the state of an entity to 'Unchanged' or 'Modified' if any entities in the graph have conflicting key values. This may be because some entities are new and have not yet received database-generated key values. In this case use the 'Add' method or the 'Added' entity state to track the graph and then set the state of non-new entities to 'Unchanged' or 'Modified' as appropriate.

My Edit method looks like this:

public override void Edit(MwbeUserData entityToUpdate)
        {
            LogChangeTrackerStateValues("UserUpdate starts");

            if (Context.Entry(entityToUpdate).State == EntityState.Detached)
            {
                DbSet.Attach(entityToUpdate);
            }

            Context.Entry(entityToUpdate).State = EntityState.Modified;

            //fix for User.Address problem
            Context.Entry(entityToUpdate.Address).State = EntityState.Modified;

            LogChangeTrackerStateValues("UserUpdate ends");
        }

I also tried code like this:

public override void Edit(MwbeUserData entityToUpdate)
        {               
            Context.Entry(entityToUpdate).State = EntityState.Modified;

            //fix for User.Address problem
            Context.Entry(entityToUpdate.Address).State = EntityState.Modified;

        }

Record which it being udpated is kept in ChangeTracker

Context.ChangeTracker.Entries().ToList()[1]

but Context.Entry(entityToUpdate).State = Detach for this object.

QUESTION 1: How to solve this?

QUESTION 2: Any good tutorial to understand how to work with EF with business n-layered applications?

Thanks for answers.

UPDATE 1: New findings:

In Repository Edit method:

Context.ChangeTracker.Entries().ToList()[1].CurrentValues["Firstname"] = "AAA"
Context.ChangeTracker.Entries().ToList()[1].OriginalValues["Firstname"]= "AAA"

but CurrentValue should be BBB, why is not updated? it was updated in Service code which calls Respority Code and updated entity is passed to Repository Edit method.

UPDATE 2:

More about my architecture: I have 3 layes Controler(WEB API), Service and Repository. So my Service method update looks like this:

 public bool UpdateUser(MwbeUserUpdateIn userUpdateData)
        {
            MwbeReturnData<MwbeUserData> userData = repository.Get(userUpdateData.UserId);

            // Determine if user exists
            if (MwbeResponseCodes.NotFound == userData.Code)
            {
                return false;
            }

            MwbeUserData user = userData.Data;

            // Check each field to be updated
            if (!String.IsNullOrEmpty(userUpdateData.FirstName))
            {
                user.Firstname = userUpdateData.FirstName;
            }

            if (!String.IsNullOrEmpty(userUpdateData.MiddleName))
            {
                user.Middlename = userUpdateData.MiddleName;
            }

            if (!String.IsNullOrEmpty(userUpdateData.LastName))
            {
                user.Secondname = userUpdateData.LastName;
            }

            if (!String.IsNullOrEmpty(userUpdateData.MobileNumber))
            {
                user.Mobilenumber = userUpdateData.MobileNumber;
            }

            if (!String.IsNullOrEmpty(userUpdateData.Email))
            {
                user.Email = userUpdateData.Email;
            }

            if (null != userUpdateData.BirthDate)
            {
                user.BirthDate = (DateTime)userUpdateData.BirthDate;
            }

            // Update Addres fields
            if (null != userUpdateData.Address)
            {
                if (!String.IsNullOrEmpty(userUpdateData.Address.City))
                {
                    user.Address.City = userUpdateData.Address.City;
                }

                if (!String.IsNullOrEmpty(userUpdateData.Address.Country))
                {
                    user.Address.Country = userUpdateData.Address.Country;
                }

                if (!String.IsNullOrEmpty(userUpdateData.Address.Street))
                {
                    user.Address.Street = userUpdateData.Address.Street;
                }

                if (!String.IsNullOrEmpty(userUpdateData.Address.ZipCode))
                {
                    user.Address.ZipCode = userUpdateData.Address.ZipCode;
                }
            }


            // Save changes to DB
            repository.Edit(ref user);
            repository.SaveChanges();

            return true;
        }

Answer 1

Instead of calling Context.Entry(entityToUpdate) and setting it state to modified you could search for the entity you want to update and modify its members. Then set its state as modified, like this.

Also in your Edit function you should explicitly list which members of your MwbeUserData object your are updating. This is a security issue, it will prevent someone over posting extra members to your controller.

Here is an example of a edit function I have used.

public ActionResult Edit([Bind(Include = "Id,CompanyName,Abbreviation,CompanyTypeRef")] Company company)
{
     if (!ModelState.IsValid) return View(company);//error invalid state

     var c = Entities.Set<Company>().FirstOrDefault(x => x.Id == company.Id);
     if(c == null) return View(company);// error could not find entity
     Entities.Entry(c).CurrentValues.SetValues(company);
     Entities.Entry(c).State = EntityState.Modified;
     Entities.SaveChanges();
     return RedirectToAction("Edit", "Company", new { id = company.Id });
}

Update: I had a similar issue with entity changes not being recorded by changes tracker in EntityFramework.Extented and it was fix by updating the entities CurrentValues with this line.

Entities.Entry(c).CurrentValues.SetValues(company);