Why Does My Entity Framework Code Throw 'New transaction is not allowed because there are other threads running in the session'?

Transaction Error While Updating Entity Framework Models

In an attempt to connect entities from two separate databases, developers may encounter the error: "New transaction is not allowed because there are other threads running in the session." This perplexing message can arise when attempting code that incorporates multiple loops and Entity Framework contexts.

The underlying issue stems from the fact that Entity Framework (EF) maintains a session for each context created. When multiple threads access the same context concurrently, it can lead to transaction conflicts. To resolve this, it's crucial to avoid modifying the same context in different threads.

In the example provided, the root cause of the error was the usage of nested foreach loops over EF queries. This approach meant that a new EF context was created for each iteration of the outer loop, resulting in numerous active sessions accessing the same context concurrently.

The optimal solution is to retrieve data from EF using a query and store it in an intermediate collection (e.g., IList). This allows the context to be disposed of and a new context created for each subsequent iteration without incurring transaction conflicts.

Here's an example of the modified code to illustrate:

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;
    // ...
}

By isolating the retrieval of data from the context, we eliminate the risk of overlapping transactions and ensure that no errors are encountered.

The above is the detailed content of Why Does My Entity Framework Code Throw 'New transaction is not allowed because there are other threads running in the session'?. For more information, please follow other related articles on the PHP Chinese website!