The Functional Programming Style

[MUSIC] 0:00 Before we get into using methods syntax with LINQ. 0:04 I wanna over a set of features in C# that fit the style of functional programming. 0:07 Functional programming languages focus on computations 0:14 as opposed to executing a series of commands. 0:17 C# is an object oriented language. 0:19 However, many of the object oriented languages out there have adopted elements 0:22 of functional programming and give us the ability to program in a functional style. 0:27 LINQ queries are inherently functional because as we write our queries, 0:32 we are expressing what we want, and not how we want it. 0:36 If all this sounds a bit confusing don't worry, 0:41 I'll show you some examples that should help clear it up. 0:44 We'll only touch lightly on functional programming for LINQ but 0:47 we'll cover it in more detail in a future course. 0:50 There are some guidelines that functional programming languages follow, and 0:54 it can be helpful to keep them in mind when writing code. 0:58 The big one is that there are no side effects. 1:01 When you run a function, 1:04 it should not modify anything outside of the function scope. 1:05 For instance, if we have a function that evaluates a collection that exists 1:09 outside the function, it shouldn't add or remove anything from that collection. 1:13 Another concept is that functions are first class citizens. 1:18 This means that functions are treated like any other type and 1:22 can be passed around as objects. 1:26 We'll be going over delegates and other function types in C# that let us do that. 1:28 We also wanna make sure that a function has the smallest scope and performs 1:34 the least amount of work possible, which is usually computational in nature. 1:38 We should be able to treat it like a piece of data. 1:43 The function takes input and gives us the result of the computation. 1:45 We could replace the function call with its expected result and 1:50 everything would run the same. 1:54 This is a good practice, in general. 1:56 But it is definitely showcased when applying functional programming concepts. 1:57 And last but not least is the use of expressions. 2:02 For instance, instead of creating a variable without a value and 2:06 then running some kind of logic to assign its value. 2:09 You use an expression to assign a value as you create it. 2:13 This concept goes very well with LINQ. 2:16 Applying these concepts in your code has huge benefits. 2:19 Your code becomes more readable, easier to maintain and easier to test. 2:23 However don't feel like you have to use functional programming just for 2:28 the sake of it. 2:32 You can take these concepts and 2:33 apply them in your applications if it's the right fit. 2:35 The goal is to help you be a better programmer. 2:38 You don't have to relearn how to program in a functional way but you can 2:41 take from these concepts and write code that's cleaner and easier to maintain. 2:45