ASP.Net Core DbContext

Author : MD TAREQ HASSAN

For ASP.Net core app

Entity Framework contexts are usually added to the service container using the scoped lifetime because web app database operations are normally scoped to the client request
if a lifetime isn’t specified by an AddDbContext<TContext> overload when registering the database context, the default lifetime is scoped
Services of a given lifetime shouldn’t use a database context with a shorter lifetime than the service

Code first approach: create entity classes and create DbContext using entity classes
Database first approach: DbContext and entity classes will be in EF core data project

For database first approach, we need to add a constructor that accepts DbContextOptions<TDbContext>

UsersDbContext.cs

public class UsersDbContext : DbContext
{
    public UsersDbContext(DbContextOptions<UsersDbContext> options) : base(options)
    {
    }
    
    public DbSet<UserModel> Users { get; set; }
}

Register in Startup

Preferred way: AddDbContextPool

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContextPool<UsersDbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("UserDBConnection")));

    services.AddMvc();
}

Normal way: AddDbContext

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<UsersDbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("UserDBConnection")));

    services.AddMvc();
}

See: AddDbContext vs AddDbContextPool

If the app uses Authentication

public void ConfigureServices(IServiceCollection services)
{

    // for Authentication and Authorization
    services.AddDbContext<ApplicationDbContext>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("AuthDBConnection")));

    services.AddIdentity<ApplicationUser, IdentityRole>()
        .AddEntityFrameworkStores<ApplicationDbContext>()
        .AddDefaultTokenProviders();
        
    // for using EF core data project in app
    services.AddDbContext<UsersDbContext>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("UserDBConnection")));

    services.AddMvc();
}

Constructor injection

FooService.cs

public class MyController
{
    private readonly BloggingContext _context;

    public MyController(BloggingContext context)
    {
      _context = context;
    }

    ...
}