How get register dbcontext in startup class for reference? - entity-framework

Question

I configure my DbContext with dependency injection in Startup, actually i need send my registered dbcontext to my class handler (EventBusExtension.GetHandlers()) but i dont know how get directly the context registered:
public void ConfigureServices(IServiceCollection services)
{
...
var dbContextOptions = new DbContextOptionsBuilder<cataDBContext>()
.UseSqlServer(Configuration.GetConnectionString("SqlServerConnect"))
.Options;
//*****************************************************************************
services.AddSingleton(dbContextOptions);
// Finally register the DbContextOptions:
services.AddSingleton<cataDBContextOptions>();
// This Factory is used to create the DbContext from the custom DbContextOptions:
services.AddSingleton<IContextDBFactory, ContextDBFactory>();
// Finally Add the Applications DbContext:
services.AddDbContext<cataDBContext>();
services.AddEventBusHandling(EventBusExtension.GetHandlers(Configuration));
...
}
How i can get and send the context to EventBusExtension.GetHandlers() ?

Answer 1

For how to get the instance in the Startup,you could use the following code:
//1.Register the service
services.AddDbContext<MyDbContext>(options =>
options.UseSqlServer(Configuration.GetConnectionString("YourConnnectionString")));
//2.Build an intermediate service provider
var sp = services.BuildServiceProvider();
//3.Resolve the services from the service provider
var myDbContext = sp.GetService<MyDbContext>();
//4.then you could pass the myDbContext to the EventBusExtension.GetHandlers()

Answer 2

The accepted anser works but as mentioned in comments and this microsoft document ASP0000 calling 'BuildServiceProvider' from application code results in an additional copy of singleton services being created.
Calling BuildServiceProvider creates a second container, which can create torn singletons and cause references to object graphs across multiple containers.
A correct way to get LoginPath is to use the options pattern's built-in support for DI.
For example to use your dbContext to get all active Host URLs to apply in CORs instead of using services.AddCors(.... you can use this code :
services.AddOptions<CorsOptions>()
.Configure<ApplicationDbContext>(
(options, db) =>
{
options.AddPolicy("AllowOrigin", builder =>
builder.WithOrigins(db.Set<MyHostsEntity>().Where(e => e.IsActive).Select(e => e.Url).ToArray())
.AllowAnyMethod()
.AllowAnyHeader()
.AllowCredentials()
);
}
);