C#: LINQ and IEqualityComparer

When writing programs in C# with the help of LINQ I have come across the IEqualityComparer<T> generic interface several times. The name conveys the purpose of the interface clearly, still, surprisingly, my first attempts to apply it were marked by strong confusion - the thing merely didn't work the way I wanted it to. Moreover, after going to Google and StackOverflow I have noticed that I'm not the only one to face difficulties with it. After inspecting multiple SO questions and answers related to the topic as well as some other articles I have both found the solution that fitted my needs for the moment and got some understanding of the way IEqualityComparer is actually used by LINQ operators. Here I will try to explain what I got from there.

 

Tutorials Are Not That Bad

From the time when I started to study programming in earnest I somehow disdained tutorials of any kind. There are dozens of them in the world of programming as well as in any other field involving operations performed by means of a personal computer. These tutorials composed of exercises or tasks, which end up being long lists of "go-there-type-this-click-that"s, sometimes interleaved with descriptions of "note-how-the-thing-changes" kind jump at you whenever you type a query involving a name of some technology or tool in Google. Moreover, almost every book dealing with some technology - a programming language, for instance, - contains such exercises. Maybe, it is even safe to say that the more exercises a book of this kind contains the better it is, so I don't state that all tutorials are useless and hardly deserve any attention and I am not even going to discuss the wide range of their quality. What I say is basically that during several years of study I used to think that an exercise inviting me to reproduce its author's actions is not worth the effort.

 

Actually, most of the tutorials, which I came across while exploring various languages and techniques, were very helpful and provided me with valuable insights, thus leaving me no reasons to lament the time spent. Furthermore, I really appreciate the work of people who produce such things just to make their knowledge and expertise accessible to others. Still, I had a reason or an excuse - the latter sounds closer to reality - to avoid tutorials when pursuing my learning goals. My explanation is as plain as possible: I merely used to believe that trying to apply a thing that is being studied to your own problems or to compose such a problem yourself for the purpose of learning and attempt to deal with it is a much more efficient approach, because it leaves a lot of room to creativity. At the same time I doubted that dumbly following the track of a tutorial can be that helpful and educating. I don't reject the idea that creativity is a rich source of both skills and knowledge, although now I barely think that the low level of creativity inherent to the process of doing most tutorials makes them bad equipment for learning.

 



Indeed, it is easy to spot a flaw in my reasoning about the educational value of tutorials. Above I have stated that following a track of an exercise dumbly wont teach you much - chances are high that this particular claim is correct. What is false is my belief that the only way to do tutorials is the stupid one, because obviously one can thoroughly inspect every step of the tutorial they struggle with and think over each action that they perform. Such an approach, even though it is guided, turns out to be quite intelligent and efficient. Moreover it seems to me that it is very difficult to do tutorials dumbly - even when I begin an exercise merely following the instructions in it, sooner or latter I find myself noting interesting features and how-to's highlighted by the author and imagining how I could use the tricks in my own solutions. So it's hard for me to accept the fact that I used to yell that tutorials are not proper learning tools.

 

It must have been my eagerness to do my own stuff, to invent things that made me reject other's expertise in the form of tutorials, but there are too many obvious benefits offered by such exercises to ignore them. First of all, their authors try hard to make one's first steps in a field as easy and as efficient as possible, so they tend to focus on the key aspects and to draw one's attention to the most important things of the technology or the tool under study. Therefore a tutorial usually provides one with understanding of the basics underlying all other matters that one is going to deal with. This is notably important whenever you explore something quite complex, incorporating dozens of features and cluttered with details, the purpose of which is hardly understandable from the first glance. Such focusing on the basics, that is delivered by tutorials and saves one from being totally overwhelmed by complexity, is made possible solely by the vast experience of their creators. Beside this, there is one more thing that an experienced teacher can give you through pages of a tutorial, and it has to do with creativity. The problem is that creativity has a dark side - the side that leads one to an invention of complex solutions to simple problems, which were, in fact, solved long ago. Unnecessary complexity of this kind is produced in huge quantities by those who study new fields and, although frequently the students learn the right way to achieve their goals later, sometimes these beasts survive in the minds for quite a long time so that later they can creep, for example, into production code. While I strongly appreciate creativity and acknowledge that even inventing a bicycle once more can be educating and worthy, I still think that when one starts to learn something new, it may be better for them to be shielded from such things by the experience of those who know the proper ways.

 

An interesting thing that I have noticed about doing tutorials while exploring SQL Server Analysis Services with the help of one is that the closer I follow the instructions in the exercise, the more it gives my. I mean that when I carefully inspect each statement that the author makes - even when some points are repeated - I end up with much better understanding, than in case I leap over instructions that seem obvious or too dull to me. Definitely, this has to do with the fact that when I skip something I risk missing minor aspects that turn out to be quite important, and this leads to holes in my mental models. These gaps, in turn, tend to produce mistakes later, but may be hard to spot at the same time. On the other hand, when deliberately examining each sentence in an exercise I focus not on achieving a goal itself, but on learning a good way to achieve it. This frees me from pressure - particularly, from the desire to complete a task as fast as possible and to leap to another problem - and allows me to keep a comfortable pace, stopping whenever I need to explore some aspect more thoroughly or think about a question. Surprisingly, learning how to achieve a goal and achieving a goal are not the same activities.

 

This said, my takeaway from the last tutorial that I have done are not only new skills and knowledge, but the obvious idea that one should not ignore other's experience merely for the sake of doing their own things and producing their own results. Experts always have a lot to say to us - newcomers - and the insights provided by their instructions may be much more valuable than the product of one's creative attempts to master something from scratch. Moreover, such intelligent and wise instructions can even spur a lot of creativity in students because they tend to provoke interesting problems and make one look for the solutions. In the end, you always learn something through facing questions and answering them - tutorials just encourage you to ask the right ones.