Above, base.OnConfiguring(optionsBuilder) calls the base implementation, which does nothing. We can remove it and specify a connection string for the database in the OnConfiguring(), as shown below. Another way to approach the issue would be to add a few more layers of complexity, introduce a queuing middleware like RabbitMQ and let it distribute the workload for you. Which may or may not work depending on why you need to introduce parallelism. But in any case, you may neither need nor want the additional overhead and complexity. In practice, and unless you actually need a distributed transaction, you should avoid using TransactionScope.
In addition, this excellent blog post by Stephen Toub on the ExecutionContext is a mandatory read if you’d like to fully understand how the ambient context pattern was implemented in DbContextScope. Remember that DbContext (just like Session in NHibernate) isn’t thread-safe. If you need to execute multiple tasks in parallel what is entity framework in a service, you must make sure that each task works against its own DbContext instance or the whole thing will blow up at runtime. This is impossible to do with the injected DbContext approach since the service isn’t in control of the DbContext instance creation and doesn’t have any way to create new ones.
ConfigureServices in API project Startup class
Entity Framework Core uses any of the following three approaches to load related entities in your application. We’ll use this class to perform CRUD operations in the subsequent sections of this article. For the DbContext class to be able to do any useful work, it needs an instance of the DbContextOptions class. Let us understand the need and use of the DbContext Class with an example. At the root directory of your project, create a folder and name it as Entities. Then, inside this folder, create two class files named Student.cs and Standard.cs.
At the application level however, a «unit of work» is a very vague concept that could mean everything and nothing. If your service method forces the creation of a new DbContextScope and then modifies persistent entities in that new scope, it must make sure that the parent ambient scope (if any) can «see» those modification when it returns. This makes creating a service method that combines the logic of multiple other service methods trivial. It’s not the end of the world but it certainly complicates DI container configuration. Having stateless services provides tremendous flexibility and makes the configuration of their lifetime a non-issue (any lifetime would do and singleton is often your best bet). As soon as you introduce stateful services, careful consideration has to be given to your service lifetimes.
There Should be Only one DbContext Instance per Request/Unit of Work/Transaction
It will use whatever default transaction isolation level the database engine has been configured to use (READ COMMITTED by default for SQL Server). And some business rules might require the use the REPEATABLE READ or even SERIALIZABLE isolation levels (especially if your application uses pessimistic concurrency control). In which case the service will need to have explicit control over the transaction scope. For certain types of applications however, the inherent limitations of these approaches pose problems. To the point that certain features become impossible to implement or require to resort to increasingly complex structures or increasingly ugly hacks to work around the way the DbContext instances are created and managed.
TransactionScope, and distributed transactions in general, are not necessary for most applications and tend to introduce more problems than they solve. EF’s documentation has more details on working with TransactionScope with Entity Framework if you really need distributed transactions. As you can see by yourself by running the SQL script below, neither Autocommit nor Implicit transactions have any significant performance impact for SELECT statements. Entity Framework’s async features are there to support an asynchronous programming model, not to enable parallelism. In a multi-threaded application, you must create and use a separate instance of your DbContext-derived class in each thread.
ASP.NET Core REST API DbContext
The only correct way to manage disposable components with a DI container like this is to significantly complicate your DI configuration and use nested dependency injection containers as Jeremy Miller demonstrates. Prior to EF6, using TransactionScope was the only practical way to control the database transaction scope and isolation level. But it brings a lot of long-term benefits for the flexibility and maintenance of the application. The AddDbContext extension method is used to register the DbContext as a service. Note how a reference to DbContextOptionsBuilder is used to configure the DbContextOptions. The UseSqlServer extension method is used to register the SQL Server database provider with the Entity Framework Core runtime.
- Which is perfectly fine for many applications but it will become a major limitation in certain cases.
- This setup suits tasks needing isolated contexts without dependencies on prior states.
- When coming up with or evaluating a DbContext lifetime management strategy, it’s important to keep in mind the key scenarios and functionalities that it must support.
- And when it comes to managing the correctness and consistency of your data — your most precious asset — magic isn’t a word you want to hear too often.
Adding a new object with Entity Framework is as simple as constructing a new instance of your object and registering it using the Add method on DbSet. The following code is for when you want to add a new student to database. A third option is to create a DbContext instance by overriding the OnConfiguring method in your custom DbContext class. You can then take advantage of the DbContext constructor to pass configuration information, such as a connection string. In Entity Framework Core, the DbContext connects the domain classes to the database by acting as a bridge between them.
Navigating the NoSQL vs. SQL Conundrum: Choosing the Right Database Solution for Your Project! 🔄📊
The DbContext acts as a bridge between the domain classes and the database. In this article we will examine how we can configure the DbContext using an instance of DbContextOptions to connect to a database and perform CRUD operations using the Entity Framework Core provider. In this article, we’ve explored how to create a DbContext in .NET with code examples. We’ve also seen how to configure the DbContext and use it to interact with a database using entity classes. By following these examples, you should be able to create your own DbContext and interact with a database in your .NET application. We’ve also defined a few methods for interacting with the products stored in the database.
You can then take advantage of constructor injection in your controller to retrieve an instance of DbContext as shown below. You can extend the DbContext class in EF Core to create your own DbContext class as shown below. To create an ASP.NET Core 8 Web API project in Visual Studio 2022, follow the steps outlined below.
A bit of context
It’s also very easy for a developer to inadvertently execute a long-running computation or a remote service call without realizing or even knowing that they’re within the context of an open database transaction. This EF behaviour can result in subtle bugs as it is possible to be in a situation where queries may unexpectedly return stale or incorrect data. On the other side, it dramatically simplifies the issue of database transaction lifetime management.
Please read our previous article, discussing How to Install Entity Framework Core in .NET Applications. The DbContext class is one of the important classes in the Entity Framework core. At the end of this article, you will understand the significance of the DbContext class in the Entity Framework Core. The primary class that is responsible for interacting with data as objects is System.Data.Entity.DbContext. In order to be more flexible and frequent with releasing new features to Code First and the DbContext API, the Entity Framework team distributes EntityFramework.dll through Microsoft’s NuGet distribution feature.
Deleting Existing Entities
Representing a combination of the unit of work and repository design patterns, the DbContext is responsible for any interaction between the application and the database in use. I’ll discuss additional aspects of Entity Framework Core in future posts here. To use the custom DbContext we implemented in the controller methods, you should take advantage of dependency injection. If you’re dealing with vast amounts of data, i.e., large datasets, you should not return the entire resultset.