C# – SqlException from Entity Framework – New transaction is not allowed because there are other threads running in the session

centity-frameworkinversion-of-controltransactions

I am currently getting this error:

System.Data.SqlClient.SqlException: New transaction is not allowed because there are other threads running in the session.

while running this code:

public class ProductManager : IProductManager
{
    #region Declare Models
    private RivWorks.Model.Negotiation.RIV_Entities _dbRiv = RivWorks.Model.Stores.RivEntities(AppSettings.RivWorkEntities_connString);
    private RivWorks.Model.NegotiationAutos.RivFeedsEntities _dbFeed = RivWorks.Model.Stores.FeedEntities(AppSettings.FeedAutosEntities_connString);
    #endregion

    public IProduct GetProductById(Guid productId)
    {
        // Do a quick sync of the feeds...
        SyncFeeds();
        ...
        // get a product...
        ...
        return product;
    }

    private void SyncFeeds()
    {
        bool found = false;
        string feedSource = "AUTO";
        switch (feedSource) // companyFeedDetail.FeedSourceTable.ToUpper())
        {
            case "AUTO":
                var clientList = from a in _dbFeed.Client.Include("Auto") select a;
                foreach (RivWorks.Model.NegotiationAutos.Client client in clientList)
                {
                    var companyFeedDetailList = from a in _dbRiv.AutoNegotiationDetails where a.ClientID == client.ClientID select a;
                    foreach (RivWorks.Model.Negotiation.AutoNegotiationDetails companyFeedDetail in companyFeedDetailList)
                    {
                        if (companyFeedDetail.FeedSourceTable.ToUpper() == "AUTO")
                        {
                            var company = (from a in _dbRiv.Company.Include("Product") where a.CompanyId == companyFeedDetail.CompanyId select a).First();
                            foreach (RivWorks.Model.NegotiationAutos.Auto sourceProduct in client.Auto)
                            {
                                foreach (RivWorks.Model.Negotiation.Product targetProduct in company.Product)
                                {
                                    if (targetProduct.alternateProductID == sourceProduct.AutoID)
                                    {
                                        found = true;
                                        break;
                                    }
                                }
                                if (!found)
                                {
                                    var newProduct = new RivWorks.Model.Negotiation.Product();
                                    newProduct.alternateProductID = sourceProduct.AutoID;
                                    newProduct.isFromFeed = true;
                                    newProduct.isDeleted = false;
                                    newProduct.SKU = sourceProduct.StockNumber;
                                    company.Product.Add(newProduct);
                                }
                            }
                            _dbRiv.SaveChanges();  // ### THIS BREAKS ### //
                        }
                    }
                }
                break;
        }
    }
}

Model #1 – This model sits in a database on our Dev Server.
Model #1 http://content.screencast.com/users/Keith.Barrows/folders/Jing/media/bdb2b000-6e60-4af0-a7a1-2bb6b05d8bc1/Model1.png

Model #2 – This model sits in a database on our Prod Server and is updated each day by automatic feeds. alt text http://content.screencast.com/users/Keith.Barrows/folders/Jing/media/4260259f-bce6-43d5-9d2a-017bd9a980d4/Model2.png

Note – The red circled items in Model #1 are the fields I use to "map" to Model #2. Please ignore the red circles in Model #2: that is from another question I had which is now answered.

Note: I still need to put in an isDeleted check so I can soft delete it from DB1 if it has gone out of our client's inventory.

All I want to do, with this particular code, is connect a company in DB1 with a client in DB2, get their product list from DB2 and INSERT it in DB1 if it is not already there. First time through should be a full pull of inventory. Each time it is run there after nothing should happen unless new inventory came in on the feed over night.

So the big question – how to I solve the transaction error I am getting? Do I need to drop and recreate my context each time through the loops (does not make sense to me)?

Best Answer

After much pulling out of hair I discovered that the foreach loops were the culprits. What needs to happen is to call EF but return it into an IList<T> of that target type then loop on the IList<T>.

Example:

IList<Client> clientList = from a in _dbFeed.Client.Include("Auto") select a;
foreach (RivWorks.Model.NegotiationAutos.Client client in clientList)
{
   var companyFeedDetailList = from a in _dbRiv.AutoNegotiationDetails where a.ClientID == client.ClientID select a;
    // ...
}

Related Solutions

C# – Entity Framework – Understanding some basics

1) The reason you are seeing a null for source.Client is because related objects are not loaded until you request them, or they are otherwise loaded into the object context. The following will load them explicitly:

if (!source.ClientReference.IsLoaded)
{
    source.ClientReference.Load();
}

However, this is sub-optimal when you have a list of more than one record, as it sends one database query per Load() call. A better alternative is to the Include() method in your initial query, to instruct the ORM to load the related entities you are interested in, so:

var sourceList = from a in _dbFeed.Auto .Include("Client") where a.Active == true select a;

An alternative third method is to use something call relationship fix-up, where if, in your example for instance, the related clients had been queried previously, they would still be in your object context. For example:

var clients = (from a in _dbFeed.Client select a).ToList();

The EF will then 'fix-up' the relationships so source.Client would not be null. Obviously this is only something you would do if you required a list of all clients for synching, so is not relevant for your specific example.

Always remember that objects are never loaded into the EF unless you request them!

2) The first version of the EF deliberately does not map foreign key fields to observable fields or properties. This is a good rundown on the matter. In EF4.0, I understand foreign keys will be exposed due to popular demand.

3) One issue you may run into is the number of database queries requesting Products or AutoNegotiationContacts may generate. As an alternative, consider loading them in bulk or with a join on your initial query.

It's also seen as good practice to use an object context for one 'operation', then dispose of it, rather than persisting them across requests. There is very little overhead in initialising one, so one object context per SychFeeds() is more appropriate. ObjectContext implements IDisposable, so you can instantiate it in a using block and wrap the method's contents in that, to ensure everything is cleaned up correctly once your changes are submitted.

C# – Entity Framework new transaction is not allowed because there are other threads running in the session, multi thread save

You should create a context for each transaction and then dispose it, you can do that like this:

using(var ctx = new MyContext()) {
    //do transaction here
}

After the closed bracket the context is disposed.

For better understanding refer to this post where you can find a great answer by ken2k. Hope you can fix you issue :)

UPDATE:

You should also try adding .ToList() to every LINQ query you have. When you iterate over a LINQ result, you can't make any changes until the iteration has finished. Check if you have something like that or share more code i.e. the piece of code where you call WriteTrace. Hope that this time this actually helps you.

Best Answer

Related Solutions

C# – Entity Framework – Understanding some basics

C# – Entity Framework new transaction is not allowed because there are other threads running in the session, multi thread save

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