How to insert/update a row using EF?

Question

What is the correct way to insert/update a row using Entity Framework?

I know this 3 methods:

1 - using Attach

var newSale = _context.ST_Sales.FirstOrDefault(x => x.SaleId == saleId);
newSale.Hours = 2;
_context.ST_Sales.Attach(newSale);
_context.ObjectStateManager.ChangeObjectState(newSale, EntityState.Modified);
_context.SaveChanges();

2 - using ApplyCurrentValues

var newSale = _context.ST_Sales.FirstOrDefault(x => x.SaleId == saleId);
newSale.Hours = 2;
_context.ST_Sales.ApplyCurrentValues(newSale);
_context.SaveChanges();

3 - using EF logic

var newSale = _context.ST_Sales.FirstOrDefault(x => x.SaleId == saleId);
newSale.Hours = 2;
_context.SaveChanges(); // EF tracks the newSale obj and knows that was changed

And to insert there are one more method witch uses the AddObject

var newSale = new ST_Sales();
newSale.Hours = 2;
_context.ST_Sales.AddObject(newSale);
_context.SaveChanges();

The problem I'm facing is an error on the EF saying that the modified row is still in memory.

My scenario:

20 users can add sales to their own company.

I have a simple table relation:

tbl_Companies { CompanyId, Name }
tbl_Sales     { CompanyId, Hours, Amount }

my Edit View simple get's a sales collection of the current week as

var model = _context.ST_Sales.Where(x => x.CompanyId == 2);
return View(model);

and on the HttpPost Action I simply loop through each one and save the db changes like

[HttpPost]
public ViewResult Index(List<ST_Sales> model)

and

bool newSale = false;
foreach( var s in model ) { // let's loop through all

    newSale = false;

    var sale = _context.ST_Sales.FirstOrDefault(x => x.SaleId == s.SaleId);
    if( sale == null) {

        // sale was not found, let's add it (this happens for todays date
        //    as there is no info yet in the db, but we need to add today's info)

        sale = new ST_Sale();
        sale.Company.Id = currentLoggedInUser.companyId;

        newSale = true;  // let's say it's a new sale so we can add the new object to the changes to commit
    }

    sale.Hours = s.Hours;
    sale.Amount = s.Amount;

    if( newSale ) {
        // it's a new sale, let's add the obj to our Entity
        _context.ST_Sales.AddObject(sale);
    } 
    else {
        // no need to do anything, EF is tracking the changes of existing objects
    }
}

_context.SaveChanges();

This works fine for one user... but if I logout and login with a different user, and I can see in the breakpoint that the companyId value is different, soon I commit the changes to be saved I get the weird error:

An entity object cannot be referenced by multiple instances of IEntityChangeTracker.

What am I doing wrong?

I'm creating a new instance in the Controller level like:

public class SalesController : Controller
{
    private SalesTrackerRepository db = SalesTrackerRepository.Instance;

    ...
}

and using the source from Sams Code

Also, I used Rick Strahl code and ending up using:

public class SalesController : Controller
{
    private SalesTrackerRepository db = 
            SalesTrackerRepositoryFactory.GetWebRequestScopedDataContext<SalesTrackerRepository>();

    ....

}

And I keep getting the same error :(

My tests are based in the same machine using Chrome and Opera with both different credentials.

How can I get this error on such test?

added... my Context is always a new one, I just don't get why I'm getting this error with diff contexts :( — balexandre, Jun 20 '11 at 17:53

score 0 · Answer 1 · answered Jun 20 '11 at 17:35

0

Your _context should be created and freed for each request, no longer. Multiple, concurrent requests should not share a context.

answered Jun 20 '11 at 17:35

Craig Stuntz

125,891
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I tried, I keep getting the same error :( I'm using this example: http://samscode.com/index.php/2009/12/making-entity-framework-v1-work-part-1-datacontext-lifetime-management/ – balexandre Jun 20 '11 at 17:46

score 0 · Answer 2 · edited May 23 '17 at 11:48

I would trying using the IDatabaseFactory from this post : Entity Framework 4 CTP 4 / CTP 5 Generic Repository Pattern and Unit Testable along with an IoC Container (Structuremap, Unity, Ninject) to scope the the instantiation of the DatabaseFactory once per Http Request.

Code should look something like this:

IDatabaseFactory.cs

public interface IDatabaseFactory : IDisposable
    {
        Database Get();
    }

DatabaseFactory.cs

public class DatabaseFactory : Disposable, IDatabaseFactory {
        private Database _database;
        public Database Get() {
            return _database ?? (_database = new Database());
        }
        protected override void DisposeCore() {
            if (_database != null)
                _database.Dispose();
        }
    }

Disposable extension method:

Disposable.cs

public class Disposable : IDisposable
    {
        private bool isDisposed;

        ~Disposable()
        {
            Dispose(false);
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
        private void Dispose(bool disposing)
        {
            if(!isDisposed && disposing)
            {
                DisposeCore();
            }

            isDisposed = true;
        }

        protected virtual void DisposeCore()
        {
        }
    }

The example you specify is using Code First style, I already have my DB in place, I already have my Entities and Repository. — balexandre, Jun 20 '11 at 18:41

score 0 · Accepted Answer · answered Jun 20 '11 at 20:03

0

Got the bugger!

I was using MemoryCache to cache some results and realized that I was using that cache to request an EntityKey.

My advise: Please check if in your project you really want to deal with all this workarounds!

answered Jun 20 '11 at 20:03

balexandre

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How to insert/update a row using EF?

3 Answers3