Dot Net What Not Posts

Like many, our database has rather a lot of naughty nullable columns that really should be non-nullable, so we end up with null data issues all over the place. One way to avoid this is to modify the property in the .edmx file to add a default value. However, this is slow and painful, and easy to forget.

As there is no use case we can foresee where you would want a null string property, we have taken the step of adding a constructor to the entity (generated in the T4 template) that initialises every string property to an empty string. This means that whenever you create a new entity, any string properties will be initialised, avoiding any null values.

However, this leaves you with a problem if you want to set a (non-empty) default value for a string.

Many of the extension methods that we use have a signature that takes an Expression<Func<TSource, bool>> rather than just a Func<TSource, bool>? Ever wondered why? Do you even know what the difference is? No, nor do most people, but it’s worth getting to know, as it can be useful.

If you’ve ever had to write or read a regular expression, you won’t need any convincing that a tool to make this easier would be useful!

If you aren’t familiar with regexs (as they are colloquially known) then it’s worth getting to know, as they can be amazingly useful at times. Sadly, they can also be amazingly difficult to write, and impossible to read afterwards!

Here are a few tips for taking away the pain.

Does this sound familiar…

User: Your app just crashed
You: What happened?
User: It crashed
You: (sigh) What were you doing at the time?
User: Using the app
You: (sigh) What specifically were you doing?
User: I was clicking in that box
You: Which box?
User: You know, the one on the window you get when you click the other button
…and so it goes on

Read how we managed to get useful information about errors without having to suffer speaking to the users!

Not a common requirement, but as it can happen, and was an interesting one to solve, I thought it worth documenting. The scenario is this: For a medical system, there are a number of treatment sites (ie bits of the human body) that must be checked. For each treatment site, there will be a number of check types that need to be done. We needed to display this information in a grid like this (this is a prototype, so only shows True and False, rather than having checkboxes that can be altered)… The treatment sites are listed in the first column, and are pulled from a database table. The interesting bit here is that the 2nd column onwards are not fixed, these are also pulled from a database table, making the grid dynamic. We don’t know in advance what columns will be needed (other than the first one of course).…

A hopefully enlightening story.

I had the need to get the latitude and longitude for UK postcodes. Knowing that another developer had recently done a lot of work doing similar things using the Google Maps API, I had a look at the code she had written. Following the Google guidelines, she had ended up adding wads of C# classes, defining the various data types that the API returns, as well as a lot of helper methods to parse the data. I had that horrible sinking feeling you get when you can see a small design requirement blow up out of all proportion.

Whilst contemplating the problem, I had an epiphany, and realised that I could solve the problem in a much simpler way, albeit with some initial effort. I thought the technique might be useful to others, but more significantly, thought that the idea of thinking outside of the box may be of interest.