Nicholas Blumhardt

The last of this curious series of journal entries today. As I mentioned previously, today is going to be about finalising the end-to-end flow of topics.

I think the first session – Fundamentals – is finished. I’m really excited and even a little nervous about putting together a new container on the fly! As a way of bedding down the terminology, mechanics and challenges, I think it is going to be great.

The layout for the remainder of the day still needs work, so I’d better get stuck into it! Those who’ve already signed up, I’ll see you soon – if you haven’t put your name down yet for either Brisbane, Sydney or Melbourne, this is probably the last reminder you’ll get from me.

A brief update today. Yesterday I think I covered everything I need to as far as demo app material goes, but tidying up, styling and (egads!) unit testing will have to wait for a rainy day.

I spent a fair bit of time yesterday looking at how I can use Whitebox to give an x-ray view of the composition process as the application is built. The information it provides is great – often revealing little issues that would otherwise go unnoticed – but the usability leaves me deeply unsatisfied. Still, it is a start, and by chipping away at it things are improving. Just having a simple view of component details is an improvement:

Today I’m concentrating on the flow of the day. I still have some questions to answer around the introductory session – how theoretical do we want to get? Does it make sense to examine the problems of composition in OO languages, or can we take that as a given for people interested in learning more about IoC? My tendency in the past would have been to go into depth about this, but by starting with “you’re going to use IoC – here’s how to do it” I think the practical side of the Dev Day will be emphasised.

Is it just me, or am I slowing down? Yesterday was a busy day of programming, but there’s still a long way to go before this application is going to cut the mustard as an example for the course.

In the end, I went with the idea of a timesheeting application. Simple material keeps out of the way, and to be honest, there is so little logic or fancy presentation in this app that it could be changed from timesheets to another example in a relatively short space of time if need be.

Up and running, we have:

• A basic MVC3 app layout
• IoC set up to create controllers
• Data access with NHibernate
• Transaction management integrated with MVC
• Logging with the venerable log4net
• A skeleton for ‘pick-me-up’ domain events

It is the last item that I’ll be working on in depth today. ‘Pick-me-up’ domain events integrate domain models with external services in a way that plays better with IoC than the thread-static DomainEvents.Raise() pattern commonly seen elsewhere.

Dispatching events to handlers is also a good example of the ‘generic handler’ pattern that’s very widely used, and registering handlers will provide some further examples for convention-based/scanning registration.

To complete the day I’m aiming to polish up the last details of the basic MVC site (for example, error handling) and bed down an example of processing work in a background process to use in the “Resources and Units of Work” session. That leaves tomorrow and Friday for more detailed work on slides, some code samples for the “Containers” session, and some reworking of the example to fit into the flow of the course.

So, yesterday, a lot of thinking. Today it’s time to start fleshing out some of the things we’ll need.

The course is going to be split into four sections, to match the natural division of the day by morning tea, lunch and afternoon tea:

1. Fundamentals
2. Effective IoC
3. Resources and Units of Work
4. Containers and Tooling

Session 1: Fundamentals

First up, we’ll set the theme of the day with some collaborative development. To introduce the vocabulary and concepts of IoC, we’ll write a simple IoC container in C# and integrate it into an ASP.NET MVC application. There are plenty of interesting design issues along the way that we’ll come back to in our discussion of containers and tooling.

Session 2: Effective IoC

The second session will introduce a ‘real’ IoC container. The focus will be on techniques and features that allow IoC to support large, complex applications in the real world. We’ll touch on all of the typical components of MVC web applications as we migrate from the simple container we built ourselves, but we’ll pay special attention to the integration between IoC and domain models because of the challenges and opportunities they present.

Session 3: Resources and Units of Work

Lifetime, AKA “resource management” can be the toughest aspect of IoC to master. We’ll take an excursion outside of the comfort of the web tier, to develop a thorough understanding of the issues involved and their solutions.

Although it is far from being ready for prime time, Whitebox will be a great way to explore the runtime behaviour of lifetime scenarios, so sometime over the coming week I’ll look at filling remaining gaps there.

Session 4: Containers and Tooling

To round out the day, we’ll use the last session to take a leisurely tour of the sights, sounds and smells of the .NET IoC ecosystem. Choosing an IoC container can be tricky business, especially when the easiest metrics to grasp, for example throughput performance, are often misleading or irrelevant. In addition to looking at some of the popular offerings and their relative strengths, I think this is where a discussion of MEF and its role will fit in nicely.

Session 4 will also give us an opportunity to examine debugging and diagnostics issues.

Today

So, what do you think?

Today’s focus for me will be to take a first cut at building the example application. I’m going to leave the ‘simple container’ design task for the event, so that we can truly do it on the fly! I want the day to be heavy on code and light on slides, so dressing up a slide deck with some guiding material will wait for later in the week.

Choosing what kind of application to build is tricky. I want attendees to be able to take something away, ideally a sample that isn’t too far from production readiness. In that respect, simpler will be better, though it can be hard to get enough breadth out of something like a ‘to-do’ or ‘timesheeting’ application. There’s some high-quality code on the web that might be reused for this purpose (e.g. FunnelWeb) so building something that mimics an existing open source application has advantages.

I’ll update you tomorrow on where things land.

Today’s the start of a really exciting week for me!

I’ve been working with Inversion of Control (IoC) Containers and related technologies since picking up Castle Windsor in 2006, actively developed Autofac for much of that time, and helped shape the first release of the Managed Extensibility Framework. In that period IoC has grown and truly blossomed in the .NET world: from its “enterprise Java” roots we’ve collectively created something that plays to the unique strengths of .NET and C#. Rather than being viewed as an esoteric fringe technology, as it was just a few years ago, IoC is firmly in the .NET mainstream and is increasingly being baked into the platform itself.

Along the way there have been many difficult questions posed, and I’ve had to ask and answer my share. It can be easy to go wrong with IoC – remember the “sharp tools” analogy of the ALT.NET movement? – especially when finding the right approach to IoC in a new situation can mean finding several wrong ways first!

Last year at TechEd Australia I presented a breakout session on IoC in .NET. Though the feedback I received was positive, I was left feeling that an hour was too little time to get many of the concepts across in enough depth. So, this year courtesy of Readify I’m going to be presenting a short course on IoC from the ground, up.

The course will be a full day, with dates in May, 2011 set for:

• Brisbane,
• Sydney and
• Melbourne.

The unifying theme will be ASP.NET MVC, but don’t be discouraged if this is not your primary platform. Much of what we cover will be independent of MVC and even of web programming in general. If you’re unfamiliar with ASP.NET MVC then it might help to brush up on that area if you want to keep up with some of the examples.

In terms of level of technical difficulty, I hope there will be something for everyone. You’ll get the most out of the day if you’re a confident .NET developer with beginner-to-intermediate experience with IoC, or if you’re an experienced user of IoC looking for broader and deeper perspectives on its use.

This week I’m preparing material for the course, and while I have a fair idea of the ground to cover, I’m interested in your ideas. I’ll be posting a progress update each day to keep you informed of where things are heading. I hope in the process I can convince you to come along, and bring your team!

More than a month has passed since the last patch release of Autofac 2.4, and enough has changed in trunk to warrant a new one. You can download Autofac 2.4.5 from the project site, or preferably, update your NuGet packages within Visual Studio.

In this release you’ll find:

• Several bug fixes and improved exception messages
• Travis and Alex have been busy making the Multi-tenant contrib package work better with the new ASP.NET MVC3 integration
• The awkward but very useful IContainerAwareComponent introduced in 2.4 has been deprecated and morphed into a much friendlier and more useful Startable implementation
• Autofac now consistently throws DependencyResolutionException (or a subclass) whenever fatal errors occur during composition

Please feel free to drop in and share your experiences on the discussion forum. For help with using Autofac, including new features, the preferred medium is Stack Overflow.