DbContextScope.EFCore

A library for managing the lifetime of Entity Framework Core DbContext instances.

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Note re package versioning: Please use the version of this library which matches your EF Core version.

For EF Core 6, the NuGet package can be found at Zejji.DbContextScope.EFCore6.

To avoid having a separate NuGet package for each EF Core version, for EF Core 7 onwards, the decision was taken to remove the EF Core version from the package name and instead have the Zejji.DbContextScope.EFCore package version number follow the EF Core version - the current NuGet package can be found at Zejji.DbContextScope.EFCore.

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This package is based on the original DbContextScope repository by Mehdi El Gueddari with the following changes:

• updated for .NET 6+ and EF Core (including replacing usages of CallContext with AsyncLocal);
• added fix for RefreshEntitiesInParentScope method so that it works correctly for entities with composite primary keys;
• added fix for DbContextCollection's Commit and CommitAsync methods so that SaveChanges can be called more than once if there is a DbUpdateConcurrencyException (see this unmerged pull request in the original DbContextScope repository);
• added the RegisteredDbContextFactory class as a concrete implementation of the IDbContextFactory interface, which allows users to easily register factory functions for one or more DbContext type(s) during startup; and
• added unit tests.

Description

Mehdi El Gueddari's original article describing the thinking behind the DbContextScope library can be found here.

In summary, the library addresses the problem that injecting DbContext instances as a scoped dependency (which ordinarily results in one instance per web request) offers insufficient control over the lifetime of DbContext instances in more complex scenarios.

The DbContextScope library allows users to create scopes which control the lifetime of ambient DbContext instances, as well giving control over the exact time at which changes are saved.

For general usage instructions, see article referred to above and the original GitHub repository readme file (a copy of which is included in this repository here). Please note the Mehdime.Entity namespace has been renamed to Zejji.Entity.

Getting Started

Dependencies

• .NET 6+
• EF Core (version equal to or higher than Zejji.DbContextScope.EFCore package version)

Installing

• dotnet add package Zejji.DbContextScope.EFCore

Dependency Injection Registrations

In order to start using this library, you will need to register several dependencies with the dependency injection container.

Standard Approach - Using the ServiceProviderDbContextFactory

In most cases you will want DbContext instances to be constructed by the dependency injection container. You will need the following registrations:

services.AddScoped<IDbContextFactory, ServiceProviderDbContextFactory>();
services.AddScoped<IDbContextScopeFactory, DbContextScopeFactory>();
services.AddSingleton<IAmbientDbContextLocator, AmbientDbContextLocator>();

Note that we use a scoped lifetime for the ServiceProviderDbContextFactory, to allow scoped dependencies to be injected into created DbContext instances, e.g. a tenant ID accessor in a multi-tenant application (see e.g. Finbuckle.MultiTenant).

If you are sure you will never need any scoped dependencies within your DbContext instances and know what you are doing, it is also possible to register the IDbContextFactory and IDbContextScopeFactory with a singleton lifetime.

See here for a discussion of dependency injection lifetimes.

Additional Customization Using the RegisteredDbContextFactory

The RegisteredDbContextFactory class can be used in rare cases where you need more control over how DbContext instances are created. Usage is as follows:

• In Startup.cs, register a RegisteredDbContextFactory instance and register one or more DbContext factory functions on that instance, e.g.:

using Zejji.Entity;
...
public void ConfigureServices(IServiceCollection services)
{
    ...
    // Create an instance of the RegisteredDbContextFactory
    var dbContextFactory = new RegisteredDbContextFactory();

    // Register factory functions for each of the required DbContext types
    dbContextFactory.RegisterDbContextType<DbContextOne>(() =>
        new DbContextOne(Configuration.GetConnectionString("DatabaseOne")));
    dbContextFactory.RegisterDbContextType<DbContextTwo>(() =>
        new DbContextTwo(Configuration.GetConnectionString("DatabaseTwo")));

    // Register the RegisteredDbContextFactory instance as a singleton
    // with the dependency injection container.
    services.AddSingleton<IDbContextFactory>(dbContextFactory);
    ...
}

See also the unit tests for RegisteredDbContextFactory here.

License

This project is licensed under the MIT License - see the LICENSE.txt file for details

Acknowledgments

Many thanks to Mehdi El Gueddari for creating the original DbContextScope library.