Explicit transaction for entire request duration with automatic commit/rollback on errors (EF6, Web API2, NInject) - entity-framework

Question

I'm starting a new Web API application, and I'm unsure how to handle transactions (and subsequent rollbacks in case of exceptions).
My overall goal is so have a single database connection per request, and have the entire thing wrapped in an explicit transaction.
I'll need an explicit transaction since I will be executing stored procedures aswell, and need to rollback any results from those if my application should throw any exceptions.
My plan was to re-use an approach I've used in MVC applications in the past which in rough terms was simply binding my database context to requestscope using ninject and then handling rollback/commit in the ondeactivation event.
Let's say I have a controller with two methods.
public class MyController : ApiController {
public MyController(IRepo repo) {
}
}
public string SimpleAddElement() {
_repo.Add(new MyModel());
}
public string ThisCouldBlowUp() {
// read from context
var foo = _repo.ReadFromDB();
// execute stored prodecure which changes some content
var res = _repo.StoredProcOperation();
// throw an exception due to bug/failsafe condition
if (res == 42)
throw Exception("Argh, an error occured");
}
}
My repo skeleton
public class Repo : IRepo {
public Repo(IMyDbContext context) {
}
}
From here, my plan was to simply bind the repositories using
kernel.Bind<IRepo>().To<Repo>();
and provide a single database context per request using
kernel.bind<IMyDbContext>().To<CreateCtx>()
.InRequestScope()
.OnDeactivate(FinalizeTransaction);
private IMyDbContext CreateCtx(IMyDbContext ctx) {
var ctx = new DbContext();
ctx.Database.BeginTransaction();
}
private void FinalizeTransaction(IMyDbContext ctx) {
if (true /* no errors logged on current HttpRequest.AllErrors */)
ctx.Commit();
else
ctx.Rollback();
}
Now, if I invoke SimpleAddElement from my browser FinalizeTransaction never gets invoked... So either I'm doing something wrong suddently, or missing something related to WebAPI pipeline
So how should I go about implementing a transactional "single DB session per request"-module?
What is best practise ?
If possible, I'd like the solution to support ASP vNext aswell
I suppose one potential solution could dropping the "ondeactivation" handler and implementing an HTTP module which will commit in Endrequest and rollback in Error... but there's just something about that I dont like.

Answer 1

You are missing an abstraction in your code. You execute business logic inside your controller, which is the wrong place. If you extract this logic to the business layer and hide it behind an abstraction, it will be trivial to wrap all business layer operations inside a transaction. Take a look at this article for some examples of this.