13

I'm tryng to save on a DB the log of a multi thread processo but I'm getting the following error: new transaction is not allowed because there are other threads running in the session.

in each tread I have this function:

 internal bool WriteTrace(IResult result, string message, byte type)
    {
        SPC_SENDING_TRACE trace = new SPC_SENDING_TRACE(
                        message,
                        Parent.currentLine.CD_LINE,
                        type,
                        Parent.currentUser.FULLNAME,
                        Parent.guid);
        Context.SPC_SENDING_TRACE.AddObject(trace);
        if (Context.SaveChanges(result) == false)
            return false;
        return true;

    }

the Context is different for each thread, but the connection with the DB is always the same.

is there a way to solve this problem?

thank you Andrea

andrea
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2 Answers2

41

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.

Community
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educampver
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  • still the same error, I have another Context for the main application (not multithread) but it is not writing when the multithread is running. can it still cause some problems? – andrea Mar 12 '13 at 17:12
  • @andrea don't have another context for your main app, try creating a context just when you need to request, add, delete or update something from your db, do it with `using` as I told you in my answer for every **single** transaction and if that doesn't fix it, add a `lock` to `context.SaveChanges()`. Hope that helps, though I'm not quite sure it does, so, good luck!!! Reply anyway please ;) – educampver Mar 12 '13 at 19:10
  • If in case I am using Repository Pattern . Then in that case what will I do? – user1006544 Nov 07 '13 at 12:58
  • @user1006544: I don't think I understand your question, what is exactly the problem your having with Repo Pattern and the solution posted here? – educampver Nov 08 '13 at 18:45
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    I had this error because I was using a loop that referred to the collection context.classname. Once I added 'ToList()' the error stopped. – John Mott Dec 22 '14 at 22:10
0

I use entity framework in a multi-threaded environment, where any thread, ui and background (both STA and MTA), can concurrently update the same database. I resolved this problem by re-creating the entity connection from scratch at the start of usage on any new background thread. Examining the entity connection instance ConnectionString shows a reader guid which I assume is used to link common connection instances. By recreating the entity connection from scratch the guid values are different for each thread and no conflict appears to occur.

// Build the connection string.

  var sqlBuilder = new SqlConnectionStringBuilder();
  sqlBuilder.DataSource = serverName;
  sqlBuilder.InitialCatalog = databaseName;
  sqlBuilder.MultipleActiveResultSets = true;
  ...
  var providerString = sqlBuilder.ToString();
  var sqlConnection = new SqlConnection(providerString);

// Build the emtity connection.

  Assembly metadataAssembly = Assembly.GetExecutingAssembly();
  Assembly[] metadataAssemblies = { metadataAssembly };
  var metadataBase = @"res://*/{0}.csdl|res://*/{0}.ssdl|res://*/{0}.msl";
  var dbModelMetadata = String.Format(metadataBase, objectContextTypeModelName);
  // eg: "res://*/Models.MyDatabaseModel.csdl|res://*/Models.MyDatabaseModel.ssdl|res://*/Models.MyDatabaseModel.msl"
  var modelMetadataPaths = modelMetadata.Split('|');
  var metadataWorkspace = new MetadataWorkspace(modelMetadataPaths, metadataAssemblies);
  var entityDbConnection = new EntityConnection(metadataWorkspace, sqlConnection);
  return entityDbConnection;
David Coleman
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