New Transaction are not allowed Entity Framework 6

Question

In an ASP.NET Webforms application on .NET 4.0 and a Web API, I attempt to add an order and orderRow to the database, but I get this error:

Error: new transactions are not allowed because there are other running threads in the session

From the client, I run an Ajax post to the controller, which has the following code for inserting a value into the database:

private readonly MyDatabaseEntities _ctx;

public ComponibileController()
{
    _ctx = new MyDatabaseEntities(@"xxx");
}

[HttpPost]
public void Post([FromBody] ComponibileCreate model)
{
    if (!ModelState.IsValid) return;

    var taskWork = System.Threading.Tasks.Task.Run(() => SaveOnDatabase(model, utente));

    ...query
    SendMailToUser(...);

    taskWork.Wait();
}

public void SaveOnDatabase(ComponibileCreate model, string utente)
{
    try
    {
        using (_ctx)
        {
            var ordine = new COM_ORDINI
            {
                ..,
            };

            foreach (var item in model.Righe.ToList())
            {
                var righe = new COM_RIGHE
                {
                   ...
                };
                ordine.COM_RIGHE.Add(righe);
            }

            _ctx.COM_ORDINI.Add(ordine);
            _ctx.SaveChanges();
        }
    }
    catch (Exception e)
    {
    }
}

I'm pretty sure the for each loop is causing the problem (especially the .ToList()). It is further described over here: https://stackoverflow.com/a/3902790/10551193 — swforlife, May 08 '19 at 15:10
if i could use async/ await i had no error but how can solve? — gigiLaTrottola, May 08 '19 at 15:16
Don't use a Task. *Don't* try to use the same context from different threads. It's not thread-safe, it's not meant to live long, just like database connections. It shouldn't be stored in a field either, unless multiple methods need to use the same instance with the same cached data — Panagiotis Kanavos, May 08 '19 at 15:34
In fact, this code can easily lead to other exceptions. If for example `SaveOnDatabase` completes too quickly, the context could get disposed *before* the other queries run, resulting in an `ObjectDisposedException`. If you want to perform multiple operations in parallel, create and use new DbContext instances — Panagiotis Kanavos, May 08 '19 at 15:35
Furthermore, the only thing that would require async execution in `SaveOnDatabase` is the call to `SaveChanges`. All other operations are local. — Panagiotis Kanavos, May 08 '19 at 15:37

score 1 · Answer 1 · answered May 08 '19 at 15:11

1

instead System.Threading.Tasks.Task.Run(() => SaveOnDatabase(model, utente)); , use

async Task SaveOnDatabase(ComponibileCreate model, string utente) {
...
await _ctx.SaveChangesAsync();
}

and call await SaveOnDatabase(model, utente) in action

answered May 08 '19 at 15:11

Lapenkov Vladimir

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Try to SaveChanges in current thread, maybe ORM can't do that – Lapenkov Vladimir May 08 '19 at 15:18
so what should i do? – gigiLaTrottola May 08 '19 at 15:21
@gigiLaTrottola upgrade to a supported framework. Really. .NET 4.0 isn't supported for years now, doesn't have TLS1.2 support which is required by everyone. Or don't try to do anything asynchronously. Request are handled by separate threads already, you gain *nothing* by using yet another thread for the query – Panagiotis Kanavos May 08 '19 at 15:33
Ok i removed the task and i wrapped the mail with a new Thread and seems works well . tks everybody – gigiLaTrottola May 08 '19 at 18:56

New Transaction are not allowed Entity Framework 6

1 Answers1