Entity framework dbcontext multiple threads. An MVC controller is instantiated per request.
Entity framework dbcontext multiple threads . NET, the DbContext is not thread safe (in any version of EF) so you cannot safely execute multiple queries (async or not) in parallel on the same context instance. I asked Daniel Roth BlazorDeskShow - 2:24:20 about this problem and it seems to be a Blazor Server-Side problem by design. EF Core doesn't support multiple parallel operations being run on the same context instance. Unfortunately this DbContext cannot be used in a Parallel. Setup Rather than have one huge DBContext, I have multiple contexts, each focused on a small area of functionality in the DB. How to instantiate DBContext in second thread? A DbContext instance cannot be accessed by multiple threads at the same time. (if "-Context" doesn't work try "--context" Entity Framework Core does not support multiple parallel operations being run on the same DbContext instance. The context cannot be used while the model is being created. The only situation where this makes sense is when you have a I read a lot about a scoped DbContext (EntityFramework) in a ASP. Multiple entity framework DbContext still leads to concurrent exception. Glorfindel. InvalidOperationException: A second operation started Create a DbContext Class; Create a Connection string for that DbContext in appsettings. A context is not thread-safe. tl;dr How can I use Entity Framework in a multithreaded . DbContext filter based on multiple values DbContext filter based on multiple values. I have proposed to my teammate another solution which can easily create multiple DbContexts as well. To log user actions, I decided to use a single method in the Project class. Entity Framework and Multi threading. My scenario: I have a class that is instantiated by multiple theads, each thread - General solution. Joined Feb 22, 2019 Messages 362 Programming Experience 10+ Aug 11, 2022 #1 I have orders and order details. I resolved this problem by re-creating the entity connection from scratch at the start of usage on any new background thread. Note that instance members of DbContext and related classes are not guaranteed to be thread safe. For this reason I have still been writing my own ORM for modular application purpose. 1,091 When multiple of these [HttpPost("filter")] requests arrive at the same time, it appears as if a new thread is created for each one. Using the same DbContext instance across multiple threads can lead The application was developed on ASP NET Core 3. It does not understand async/await AFAIK, and should not be used with the Entity Framework async extension methods. NET 4. and this article. This does not mean you cannot have multiple threads each with their own copy of the db context. WhenAll( In Entity Framework Core (EF Core), thread-safety checks are built-in diagnostics to warn developers when theyβre using DbContext instances in a potentially unsafe multi-threaded manner. In this article DbContext pooling. Says a Entity Framework Core does not support multiple parallel operations being run on the same DbContext instance. These threads are consumers of the tasks table and remove and update tasks from it. It makes sense to setup the DI framework with a scoped DbContext, due to have one DbContext per request. If your Action Unhandled Exception: The context cannot be used while the model is being created. 1 Alternative To Passing A DbContext object To Parallel Task. Period. This includes both parallel execution of async queries and any explicit concurrent use from multiple threads. It's common to have only one DbContext for the entire application. Multi-thread. Always put a DbContext in a using statement if you can. NET 5. Its important to not that - "Entity Framework Core does not support multiple parallel operations being run on the same DbContext instance. Simply make your application DbContext inherit from ThreadSafeDbContext and I have a question guys, what would happen if I (using Entity Framework) call SaveChangesAsync() multiple times simultaneously? Just make sure they don't try to update the same row in the database. The DbContext class will work fine with async as long as you are using EF6 or higher; however, you can only have one operation (sync or async) per DbContext instance running at a time. Just be certain if you do this that the concurrent processes are unique so you don't have concurrency errors. However, each context instance does set up various internal services and objects necessary for performing its duties, and the overhead of continuously doing so may be I have researched this, and I agree that DbContext is not thread-safe. Although it seems like you're only passing entities to other threads, it's easy to go wrong at this, when lazy loading is involved. I know it's not thread safe so I'm using locks where I need to. 1 How to use DbContext in multi-threaded app. Entity Framework Core is an open-source, popular, lightweight, and flexible cross-platform ORM. What if I use two separate entity contexts, one for each thread (and call SaveChanges() on each) - will this be thread-safe? // this method is called from several threads concurrently public void IncrementProperty() { var context = new MyEntities(); The correct way is simply to instantiate a new DbContext for each thread that needs to perform a database operation, just like each thread needs its own database connection. Things that I have tried: 1. If you're using . The DataContext class is part of LINQ to SQL. If code in these threads need to use the database, they will all use the same ambient DbContext instance, resulting the same the DbContext instance being used from multiple threads simultaneously. NET Core API application even though DbContext is not threadsafe? Context I am working on a . It's more like multi-tasking, although it often looks the same. Never call an instance of a DbContext from multiple threads (they are not thread safe). This exception may be thrown if the context is used inside the OnModelCreating method or if the same context instance is accessed by multiple threads concurrently. So you should not use them over multiple threads. public async Task<IList<MyObject>> GetAll(MyContext context) { return (await Task. Multithreading This is usually caused by different threads using the same instance of DbContext. How to handle DBContext instancing in a third one could be one context per thread in a form of. In addition, if we do not await the action, we will also end up with multiple threads trying to use the same DbContext instance concurrently, which could result in exceptions like the one we discussed earlier. So if you have at least two components in the same page which are trying to execute an async query then we will encounter the exception:. I have been reading about the quirks I could find when having some threads working on the same table with entity framework core and I have noticed that DbContext is not thread save With EF. Thus if you use one DbContext per request, you're safe as long as you don't manually spawn threads in your controller actions (which you shouldn't do anyway). Like the majority of the types in . g. Your method is thread safe while each DbContext is accessed from different thread. This includes both In concurrent environments, making your Entity Framework `DbContext` thread-safe is essential to ensure data integrity and avoid race conditions. Improve this answer. Share DbContext among threads. I really like the new Task library in . Solved; Besides, the reason DbContext doesn't allow concurrent calls is that it's a Unit of Work, not a connection, and actually tracks and controls the objects it loads or persists. AddDbContext<ApplicationDbContext>(options => Entity Framework Core does not support multiple parallel operations being run on the same DbContext instance. With the creation of a different data context for each request, the ability to synchronize the data contexts across multiple threads now works without synchronization errors. Thoughts on Entity Framework 5 and Multi-Threading. I read, that SQLite supports three different threading modes: Single-thread, Multi-thread and Serialized. Object was not found in the ObjectStateManager. To save data into the DB, we call dbContext. NET Core API app exposing several RESTful inte This statement means that it's not safe to access a DbContext from multiple threads in parallel. InvalidOperationException A DbContext is a Unit-of-Work and multi-entity Repository, not a database connection or model. In this mode, all mutexes are disabled and SQLite is unsafe to use in more than a single thread at once. CreateInstance() creates a new instance using the same connection I'm using Entity Framework as my way of communicating with the database and fetching/writing information on it, on a ASP. allowing every worker process (thread) to have a new instance of the DbContext class, I'm doing this because the DbContext class is not thread safe. Entity Framework : how to work with Entity Framework Core (EF Core) is a popular ORM in . The real problem starts when I go to update or create something it says . ForEach and it's hugely improving the performance of my code, but I'm curious about DbContext with multiple threads. json; Add the DbContext to your configured services in Startup. SaveChanges() method acts like a commit on a regular database system (RDMS). A second operation started on this context before a previous operation completed. Which means, just for sure, never use it in multiple threads anyway, even if they don't run parallel. EF Core uses a DbContext, which represents a session with the database and is responsible for tracking changes, performing database operations, and managing database connections. β Multiple entity framework DbContext still leads to concurrent exception. I need to read and write from/to a tasks table from multiple threads. Entity Framework Core does not support this scenario either. Multiple thread in EF 5. They all connect on the same DbContext, and the next query starts before the previous is completed. It's a client-side, disconnected Unit-of-Work and multi-entity repository. ForEach to do work on multiple threads, using a new EF5 DbContext for each iteration, all wrapped within a TransactionScope, as follows:. Especially in web farms you have limited number of databases β Thread Safety: DbContext is not designed to be accessed by multiple threads concurrently. DbContextFactory you can resolve easily your DbContext dependencies in a safe way injecting a factory instead of an instance itself, enabling you to work in multi-thread contexts with Entity Framework or just work safest with DbContext following the Microsoft recommendations about the DbContext lifetime. This threw me when I first discovered it; it also Correct. NET Core DI to be clever enough to create a new DBContext to handle each thread separately, but clearly this isn't the case. However, in some scenarios, a developer might be certain that their usage is Entity Framework : how to work with multiple instances of DbContext across multiple threads. When multiple threads try to access the DbContext simultaneously, I am getting various exceptions such as. I am trying to create a console application where I am trying to use Entity Framework to dynamically create database and tables to store the data. The only two shared (between entities) mutable resources in a dbContext are the connection and change tracking (caching). Multiple entity A DbContext isn't a database connection. The underlying database connections are pooled and will be reused. Only one of those can be open at a time. Therefore, always await async calls immediately, or use separate DbContext instances for operations that execute in parallel. Thats hard to beleive it forces single application to use single database. Never use the same context from multiple threads - just create separate one for each parallel operation. Just make all changes (which Entity Framework will cache) and then save all of them at once calling SaveChanges() after the loop (outside of it), like a database commit command. And HttpClient handlers are meant to work on the messages, not execute business code or access databases Entity Framework Core: different threads using the same instance of DbContext. NET that allows you to work with SQL databases. It tracks all changes made on the client side and only opens a connection when SaveChanges is called to persist all of them in a single transaction. In Entity Framework Core (also called EF Core), a Db context is an object that coordinates queries, updates, and deletes against your database. Why re-initiate the DbContext when using the Entity Framework? Share. Share. Solution 2: DbContextFactory. However it is questionable if you would gain any benefits instead of running queries one after the other. Entity Framework Core does not support multiple parallel operations being run on the same DbContext instance. - vany0114/EF. EF core DbContext in a multithreaded API application. AddDbContext<ApplicationDbContext>(options => options. Running Multiple Entity Entity Framework provides async versions of most database operations, such as `ToListAsync`, `FirstOrDefaultAsync`, etc. DbContextFactory I am using Parallel. I'm sure Entity Framework's connection pooling is smart enough but I'm wondering if I should add any parameters to limit the number of threads I'm a bit new when it is coming to Entity Framework 6 from the old style of ADO. A DbContext is generally a light object: creating and disposing one doesn't involve a database operation, and most applications can do so without any noticeable impact on performance. The three other action methods in the controller demonstrate three options for fixing such a Avoiding DbContext threading issues. Or between instances of the same classes in different threads. Single-thread. Different DbContext instances will be instantiated for every request, and different DbContext instances should work from different threads just fine. A DbContext instance isn't thread-safe: you should never ever use it in parallel threads. NET, so bear with me here. Using any context. Now, I know that by default the Entity Framwork DbContext is not thread-safe, so I know I should do something to make it thread-safe, but I just don't know how to do this. 0), with Entity Framework Core, is it safe to dependency inject a DbContext instance for each thread? It depends. Thread safe Entity Framework 6. So never ever address a context from multiple threads and don't jump through hoops to try and make it thread-safe. Since a singleton service is shared across the entire application, it can be accessed by multiple threads The underlying database connections that the Entity Framework are using are not thread-safe. You can execute only one query at a time otherwise you will get an exception like you did above. However instead of injecting DbContext you can inject DbContextFactory, use it to create two DbContexts and then execute queries in parallel and await the result. Let's start by echoing Ian: Having a single DbContext for the whole application is a Bad Idea. Multiple Errors Related to Threads During Entity Framework Transaction. Entity Framework: How to prevent dbcontext getting accessed by multiple threads? 0. raysefo Well-known member. Setting the DBContext, Repository and Service lifetimes to "Transient". Running Async Calls with DbContext in Entity Framework. Currently, each method has SaveChanges() from DbContext called at the end which means for every model, one call will be invoked. Using a DbContext across multiple threads can lead to unpredictable results and hard-to-debug issues. I believe that the dbcontext shouldn't be shared between multiple threads - I remember reading about that somewhere, but I can't find the link. 5. your MqttClientHostedService) are resolved only once for the In addition to answer by Matt Bommicino which explains lifetime of dbcontext in Blazor app. See point 1 and 2 respectively; If you find your self wanting to throw more threads at your Database (to speed it up), you are likely doing something wrong. You have seen how to use Entity Framework data contexts across single threads and multiple threads without causing threading conflicts. Extensions methods may be thread safe, and may be thread unsafe depending how you write them. In general, parallelizing database access within a single business transaction has little to no benefits and only adds significant complexity. Suppliers. You must never Entity Framework is not thread-safe. It is not meant to enable parallel execution using the same DbContext. In order to support multi-thread environment, I had to initialize a new DbContext based on a connection string every time a communication with SQL is needed. Multiple Concurrency access to DbContext in Webapi. The database connections it uses don't allow multiple concurrent queries because the databases don't allow that, at least not with tricky coding that doesn't actually execute stuff in parallel. Until then, there's no connection. 20. NET Core environment. ForEach loop (or any kind of thread). Follow edited Feb 7, 2021 at 7:21. Concurrency across a scoped DbContext. Open the package manager and run the 2 lines above. You use it like the following where as db is the original DbContext and db. The context objects generated by Entity Framework are not thread-safe. The DbContext is not thread safe, meaning you cannot share it across multiple threads. The pattern I propose does use multiple threads, but a single DbContext is only every accessed by a single thread in a single-threaded fashion. I suggest, entity framework to support multiple dbcontexts in same database by naming convention. And since ASP. Ask Question Asked 11 years, 3 months ago. The stack overflow answers you already referenced, explain this. The source of the problem is that MyContext is held captive as a Captive Dependency in the following object graph:. The entity framework DbContext and ObjectContext classes are NOT thread-safe. Entity Framework Core: different threads using the same instance of DbContext. BeginTransaction() In my code, the . I am working on a . Serialized. Just have your background processes create a new DbContext in a using block. Make sure that you have the necessary dependencies and target framework version set correctly. Please see this StackOverflow thread: Is DbContext thread safe? The DbContext is not thread-safe, but you can instantiate a new one for each thread. I'm using SQLite with Entity Framework Core (RC1). Using DbContext in Parallel. So, let's imagine that here I'm dealing with functionality for working with People. As the DbContext itself is not thread-safe, I have tried to create a new DbContext together with its options in addition to obtaining a DbContext from an IServiceProvider. Entity Framework dbcontext crashing during foreach loop. Then multiple DbContextinstances can run on different threads. I have run into a scenario where I had to do parallel operations on entities in one context. Database. The `DbContext` class in Entity Framework is not inherently thread However, If we are looking for a simple method for managing isolated DbContext instances, AddDbContextFactory is a better choice. EF core DbContext in a Entity Framework Core (EF Core) is a popular ORM (Object-Relational Mapping) tool used in . NET Core API app The first API in BooksController (ModifyBooks) will, by design, fail because it incorrectly uses a DbContext on multiple threads simultaneously. c# entity framework with threading. I agree with others. An MVC controller is instantiated per request. Context. To do this, I gave each thread a db context scoped to that thread. Take a look at Entity Framework and Multi threading. DbContext is not thread-safe. R. Similar threads. I code as if it's multi-thread, but the framework takes care of how many threads it actually uses. NET applications for data access. NET for that. I suppose that you use your repository multiple times during the same request in parallel that's why you get the exception. DbContext default lifetime is set to Scoped. NET Core worker automatically creates a multiple threads and I don't think I can control it. ","ExceptionType":"System. 25. For more information on how to avoid threading issues with DbContext. NET Core API application even though DbContext is not threadsafe?. MqttClientHostedService -> PositionService -> UnitOfWork -> MyContext All types in this graph are registered as Transient, but still, services that act as hosted service (e. Use multiple schemas with multiple contexts if possible. Id). Note that instance members of DbContext and Multiple entity framework DbContext still leads to concurrent exception. This is reasonable restriction, cause DbContext is not really thread-safe class. 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. You can If you mean you are using the same dbContext instance from multiple threads, and even doing multiple SaveChanges in parallel - don't do that. be thrown if the context is used inside the OnModelCreating method or if the same context instance is accessed by multiple threads concurrently. Modified 10 years, As far as I can tell. Using Visual Studio 2013 Entity framework wizard, I created a code-first by reverse engineer a Indeed you cannot save changes inside a foreach loop in C# using Entity Framework. 1. Entity framework 6 fails on multi tasks. (. β Poul Bak. If "simultaneously" means by multiple threads then you can't do This exception may be thrown if the context is used inside the OnModelCreating method or if the same context instance is accessed by multiple threads concurrently. 3 I'm not clear why this is happening, as while I'm aware that DBContext is not thread-safe, I would have expected . tl;dr How can I use Entity Framework in a multithreaded . 0 Share DbContext among threads. References. Here's an example: If you must share a Or between instances of the same classes in different threads. NET pools threads, instances that are And I found that my issue somehow is similar to this: SqlException from Entity Framework - New transaction is not allowed because there are other threads running in the session. 5 and EF 6, then you can use the new Async() methods to automatically use multiple threads for all of that. I'm trying to create a new WPF MVVM project and also a few WinForms that will use just straight out DBContext without data-binding with the EF 6. One thing to bear in mind about using entity framework is that the DbContext object is not thread safe. (Enabling Multiple Active Result Sets you can remove this restriction, but it's not good decision cause To use these extensions, install the nuget package for your C# project and ensure that the appropriate namespaces are referenced. ToArray(); } In case this helps anyone: In my case, I did ensure that the non-thread-safe DbContext had a TransientLifetime (using Ninject), but it was still causing concurrency issues! Turns out that in some of my custom ActionFilters I used Dependency Injection to get access to the DbContext in the constructor, but ActionFilters have a lifetime that keeps them instantiated I am building my own custom repository, based on entity framework, and I'm creating some extension methods that allow me to save partial view models as entity models so I'm building my own Add and Update methods. All the threads would compete for resources such as memory with other threads necessary to server other concurrent requests. The lead is telling me that DbContext is essentially a singleton under the covers and this code would ultimately mess up the database. XyzAsync() method is only useful if you either await the called method or return control to a calling thread that's doesn't have context in its scope. DbContext is not thread safe so you can not run parallel queries. " This includes both parallel execution of async queries and any explicit concurrent use from multiple threads. NET CORE application. 2. Faced the problem of using one singleton dbContext from different threads. NET project that uses Entity Framework and I am encountering threading issues with my DbContext. 26. This includes both parallel execution of async queries and any If code in these threads need to use the database, they will all use the same ambient DbContext instance, resulting the same the DbContext instance being used from Have a read of this blog also have a read of this article about Entity Framework specifications for its async pattern support. Entity Framework . If your idea is to have one DbContext per web request, and the consistency of your application depends on it, having one DbContext per thread is a bad idea, since a single web request can still get multiple DbContext instances. Async tasks on different dbContexts. If you don't create a transaction per request you can simply make repository Is it possible to use parallelism in Entity Framework's DbContext? Basically I have an application that adds thousands of records for each of the 4 tables that I have. This means that under the covers the entity will callback to the context to get some Entity Framework DbContext is not thread safe. 7. Thread starter raysefo; Start date Aug 11, 2022; R. The DbContext itself is not threadsafe! I'm using Parallel. This is usually caused by different threads using the same instance of DbContext. With EF. You can simply wrap your code in a TransactionScope and start each Task with an action that creates its own context and saves its changes: Accessing the database from the same thread processing the request is trivial, but when spawning threads that requires their own DbContext, this turns out to be tedious. 4. In this mode, SQLite can be safely used by multiple threads provided that no single database connection is used simultaneously in two or more threads. GetConnectionString("DefaultConnection")), Of course, that doesn't really depend on more than one thread. Entity Framework : how to work with multiple instances of DbContext across multiple threads. 0. The underlying cause of this is the fact that DbContext operates on DataReader. Select(s => s. NOTE: This answer talks about the Entity Framework's DbContext, but it is applicable to any sort of Unit of Work implementation, such as LINQ to SQL's DataContext, and NHibernate's ISession. Using a proper DI container, the solution would be to setup the DbContext with a Transient lifetime : services. Using asynchronous save changes on In entity framework, DBContext is not thread-safe. 3. c# working with Entity Framework in a multi threaded server. How do I set in run-time, which mode I want to use with my database? This exception may be thrown if the context is used inside the OnModelCreating method or if the same context instance is accessed by multiple threads concurrently. Wpf: using separate dbcontext in application lifetime. cs; Setup the DbContext in the controllers that will use it. I've seen some solutions for that like detaching and attaching the entity. As long as you create a new context (and dispose of it) on the background thread and not try and use the one from your main application thread, you will be fine. Hence, you should not use multiple threads to access a DbContext instance simultaneously. UseSqlServer(Configuration. using (var transaction = new TransactionScope()) { int[] supplierIds; using (var appContext = new AppContext()) { supplierIds = appContext. context. Basically it's just a suffix on any of the methods. usjf sejshg gkwsv cjwc ksrwopvcl sfhxsxp kdi uzikxsm hyocym dnyztr ioqhky yxkyrwsv ubgxzztd szsikedgf gfskryz