DDD, TDD, Enterprise Library, Autofac, and Lokad.Shared libs!

So my project has been chuggin along quite nicely, and gave my CTO a quick look over the design of my project of which he was very impressed...I'm glad I spent all that time reading up on DDD, BDD, TDD, and listening to all the ALT.NET podcasts. I've learned SOOOOO much in the past month it is ridiculous, mostly thanks to coming across ALT.NET, and then reading everything linked from that source. I can honestly say I'm 100% sold on the TDD approach. Initially, after reading about it I was like, hmmm, yeah, I can see that working, but writing tests first kinda seems dumb and redundant. After all, obviously you know the tests will pass because you wrote them!! Then...I saw the light!!! I'm currently prototyping my project, but since I live in the real world I can reasonably assume the prototype will become the real thing. But that's not really an issue having designed everything with DDD and DI. Once the prototype is done, we can optionally replace the implementation, change the IoC wiring up, and voila, it just works (because we had all those tests written). Another design choice for the prototype I made was to use DB4O rather than SQL Server. DDD emphasizes very much on storing aggregate roots in repositories, and let's be honest, object databases work ridiculously well with storing domain entities. So not only can I speed up development in my prototype by having all repositories go to a DB4O backing store, if it's decided we need to change to a relational database, boom, I just need to reimplement all my repositories with NHibernate. And just to drive home how easy DB4O is, literally, this is what you need to do to store a User in the database.
using (IObjectContainer c = Db4oFactory.OpenFile("database.db"))
Seriously!!! It IS that easy! But back to why I'm sold on TDD. Originally, I had IUsersRepository modeled something like this:
User GetUserByName(string userName);
User GetUserById(Guid id);
User GetUserByFirstName(string firstName);
And then I realized, it's a total pain in the butt to be adding all these methods because once the method call reaches the DB4O container, I need to pass in a predicate for the query. So I thought, I'll just pass the predicate directly to DB4O. I changed all my repositories (I had 4 at the time), to do this instead:
User GetUser(Predicate<User> condition);
So now I can simply do this:
var user = usersRepository.GetUser(x => x.UserName == userName);
I've converted 3 methods (and potentially more) into a single method that is very expressive and easy to read (thank you lambdas!). And then I reran all my tests and they passed....which leads to the following conclusion: TDD lets you refactor with confidence! Oh wait, I mentioned Autofac and Lokad.Shared libs in this blog post didn't I.... To start...my project has removed all dependencies on the Enterprise Library. In my previous post I mentioned how Unity wasn't as mature as other frameworks. Well, it appears that the Logging Block and/or the Exception Handling Block has a dependency on Unity. I definitely did not like having 2 IoC containers in my bin directory, so I decided maybe I should just ditch the entire thing. Honestly, I didn't really like the EntLib anyways....the logging block requires the use of a static class Logger (tight coupling), and the exception block needs a try/catch/handle for any exception you want to handle, again with a static class ExceptionPolicy (more tight coupling!!!). So now it was a matter of finding a replacement. There really was only 2 choices: the Castle Stack, or Autofac+Lokad.Shared. I was not very impressed with the lack of documentation on the Castle Validator component (or even where to download a binary of it). Also, I'm really not a big fan of attributes on parameters. So what's left is Autofac and Lokad.Shared. I chose Autofac mainly because I love its lambda syntax (and the included performance benefit). But of more concern is Lokad.Shared. a) It is basically written by 1 guy b) It doesn't have community inertia But after reading the examples here and here I didn't have a choice! It is just too damn nice! Comparing code I'm writing today with code I wrote 3 months ago is like light and day....on different planets. And since I'm very link happy today, check out this awesome add-on called Studio Tools. It's free, only 1.9 megs and has the most impressive and blazing fast file/class/symbol search I've ever seen.


There's a few of us floating around who've found, like, and use Lokad.Shard (and Lokad.ActionPolicy).