Dot Net What Not Posts

One of my first posts on this blog was about the problem of using anonymous types when you want to send the data outside of your current class. At the time, the only way I knew to solve this was to create a simple class that had the structure of the anonymous type, and create one of these instead of the anonymous type. I do this regularly, although I have taken to naming such classes CustomerOverview, OrderOverview, etc, instead of CustomerTmp as I did in that blog post, as they aren’t really temporary classes at all, they are slim, flattened overviews of the class.

This approach works well, but it can have its downsides. One, as mentioned in that post, is that it is easy to end up with a proliferation of classes, many of which may only be used in one location in the code. If the classes represent lightweight views of entities in the model (such as the two examples shown above), then I don’t worry about this, as it is clear what they represent, and it’s fairly certain that I’ll end up using them somewhere else at some point.

I previously blogged about a seemingly innocent LINQ problem that had me baffled for ages, which was how you sort or filter an entity’s child collection in Linq. For example, if you want to pull a collection of customers, and include all of their orders from this year, but none from earlier, then there doesn’t seem to be a simple way to do this in Linq. You need to do the query in two stages, the first which builds an anonymous type, and the second which links the to parts of it together. See that post for more details.

I also blogged about the problem of Linq not including child entities when doing joins, which requires you to cast the query to an ObjectQuery<> so you can use the Include() method on it.

The problem comes when you want to combine the two methods, meaning that your query needs to be constructed in two stages to ensure that the sorting or filtering of the child collection is done correctly, but you also need to cast the final result to an ObjectQuery<> before you send it out over WCF. The problem arises because you need to enumerate the query before doing the Include(), as that is the only way to ensure that the sorting is done, but calling AsEnumerable() gives you an IEnumerable<> (reasonably enough), which can’t be cast to an ObjectQuery! So what’s a fellow to do? Good question, and one that had me going for ages.

I am currently working on an application where I want to have a search feature that allows people to search for businesses within a certain distance of their home (or anywhere else they care to choose). I have some old UK postcode data knocking around, and was going to use that. For those not familiar with them, UK postcodes are made up of two parts, a major (also known as “outward”) part, and a minor (or “inward”) part. The major part is one or two letters followed by one or two digits, and the minor part is a digit, followed by two letters. Examples of valid postcode formats are M25 0LE, NW11 3ER and L2 3WE (no idea if these are genuine postcodes though). Coupled with the postcodes are northings and eastings. These odd-sounding beasties are simply the number of metres north and east from a designated origin, which is…

Of course, we professional programmers never make mistakes, ahem. That’s why we never need to use debuggers, ahem.

Well suspend belief for a moment, and assume that I had a bug in the code I was developing. You know the feeling, you stare at it, you write unit tests, you stare at it some more, and still can’t work out why on earth Visual Studio is claiming that there is an error in your code, when it’s so obvious that there isn’t. You even get to the point of talking to your computer, pointing out the error of its ways…

Sadly, whilst building a solution yesterday, my machine started behaving in a very weird manner, with applications not responding, the taskbar disappearing and so on, followed by the dreaded blue screen of death. When I checked the event log after pulling the plug out (I hate doing that!) and rebooting, I found lots of errors, which led me to a Microsoft Connect article (now sadly removed) where someone was reporting a very similar problem.

To my amazement, the very last comment by a Microsoft employee in response to this bus report was “This is known issue, this bug was resolved by mistake, we are already addressing this issue.”

Surely they didn’t mean that did they? Someone tell me I read that wrong!

As the non-existent avid reader of this blog will know, I’m far more interested in learning new technologies than I probably should be, given the limited amount of time I have to learn them properly! With that in mind, I shouldn’t be looking at yet another, but this one does have a very immediate benefit (honest).

I have been an ASP.NET developer for quite a number of years, and can knock out a complex web site fairly quickly. However, as with most of my other programming until recently, this has always been along the “throw it all in the code-behind” anti-pattern. I’ve come a long way in the last six months or so, and am now very comfortable using MVVM in WPF, and separating out my code into logical classes as all the Good Programmers do.

Logically therefore, my web site development should follow the same lines. I read up on both MVC and MVP, and came to the conclusion that as an experienced ASP.NET developer, MVP made a lot more sense to me. I couldn’t honestly see any technical benefit of one over the other, mainly as the MVC proponents seem to raise the same old “webforms are evil” arguments, without any real justification (to me at least, they obviously feel justified). My own feeling was that MVP wins out because it completely isolates the view from any action, meaning that the view is as dumb as it can get, which makes unit testing a doddle. I was won over towards the Passive View version of MVP, as this has even less code in the view than the other flavours.

This is not to say there’s anything wrong with MVC, just that I feel more comfortable with MVP.

This post details my initial exploration of WebFormsMvp.