Left fold

Let's get back to my series on the evolution of the C# language. Everybody is familiar with what a delegate is, right? We know that delegates are a big part of the events system in .Net. We register a method on that delegate ( called handler ) that is invoked when the delegate is invoked. In other words, a delegate simply points to a method. The advantage here is that, as the delegate wraps the method and is an object, we can simply pass it to a method as a parameter! Think about this: This is how we use a delegate in events, for instance. The class exposes the delegate and we register our method to listen it. When the delegate is called inside the class, all the registered methods will be called (because of this, we call it a Multicast Delegate ). This works well, because all you have to do is have a method with the required signature. In the example above, we needed to declare two methods just to make a Console.WriteLine. Isn't this too much? I think it's a bit to...

It's 3 am and i don't feel like sleeping. I've been helping a friend to work on his code and now i'm only partially tired. Well, why not continue with my series on the evolution of C#? Let's do it! So, this time i'm going to talk about nullable types . Everybody used them already, but back in .Net 1.0 they didn't exist. How did you represent a "no value present" value? Sure, string can have null, but null is different than empty, right? How do you represent an empty numeric type then? You check if it is bigger than 0? Well for some cases that's just how developers did it. Either that or create a constant value that represents a "no value". But, to me, that is not expressive enough . Basically, a nullable type is only a non-nullable type wrapped in the System.Nullable struct. This is a generic struct, so it makes use of the Generic features of C# 2.0. The struct is very simple, it contains only a HasValue and a Value proper...

It's been a while since i wrote the last post, but i did not forget my purpose of creating a series that shows the evolution of C#. Today i came here to talk about one of the most useful features of C#, even if you dont know you're using it. Let's talk about iterators ! What is an iterator? For those of you who didn't read about the iterator pattern somewhere in the internet or in the "Gang of Four" book, you can read a description  here . The iterator is a class/object/whatever which knows how to traverse a structure. So, if you have a list or collection of objects, an iterator would have the knowledge of how to traverse that collection and access each element that it contains. The iterator is a well known design pattern and is behind many of the wonderful that we have nowadays in .NET (Linq comes to mind). Why is it a feature? Truth be told, an iterator is a concept well known way before .NET even existed. Being an OO Design Pattern, the iterator has...

Today, let's look at a simple trick with strings in C#. It may be too obvious and repeated around the internet, but nevertheless i want to give my 2 cents on the subject. So, let's start! Imagine you have a list of any type and now you will need this values separated by a comma in order to be processed in some stored procedure. The desired output for a list of  {1,2,3,4} is a string like this "1,2,3,4" . How will you solve this problem? I've seen and done multiple approaches. Let's order the possible solutions (in my mind) from the most complex to the simpler. First, we can do: Notice how complex this can be, and how fast it can become messy. When replicated across an entire project (imagine the nightmare of having this replicated in your Data Access Layer whenever a stored procedure needs this input), this can be a pain. Of course, you could extract the behavior and create an extension method for it, but as we will see, it is not necessary. Our second...