WEBVTT 1 00:00:00.160 --> 00:00:03.200 Imagine hiring a contractor to build a house for you, 2 00:00:03.960 --> 00:00:06.799 but instead of just handing them a beautiful blueprint and 3 00:00:06.879 --> 00:00:09.279 letting them get to work, you are basically forced to 4 00:00:09.320 --> 00:00:10.519 stand right next. 5 00:00:10.279 --> 00:00:12.119 To them, just watching their every move. 6 00:00:12.279 --> 00:00:14.880 Exactly you're telling them exactly what angle to swing their 7 00:00:14.880 --> 00:00:17.839 hammer for every single nail. You know, you have to 8 00:00:17.960 --> 00:00:20.559 dictate how much force to use, which hand to hold 9 00:00:20.559 --> 00:00:23.719 the nail with, and even like when to take a breath. 10 00:00:23.839 --> 00:00:26.160 It sounds absolutely exhausting, right. 11 00:00:26.280 --> 00:00:28.800 But for a very long time, that is essentially what 12 00:00:28.800 --> 00:00:31.079 writing software was like. You didn't just tell the computer 13 00:00:31.160 --> 00:00:35.600 what you wanted. You had to meticulously choreograph every agonizing 14 00:00:35.640 --> 00:00:38.280 step of how to actually get there. 15 00:00:38.399 --> 00:00:40.920 Yeah, and that is a phenomenal way to frame the 16 00:00:41.000 --> 00:00:45.000 history of programming, because the evolution of a language it 17 00:00:45.039 --> 00:00:48.240 isn't just about adding new buttons to the dashboard. It's 18 00:00:48.280 --> 00:00:53.560 a relentless march towards stripping away that tedious mechanical choreography. 19 00:00:52.960 --> 00:00:54.640 All that extra baggage. 20 00:00:54.240 --> 00:00:57.479 Exactly what we often call the fluff. The goal is 21 00:00:57.520 --> 00:01:00.719 so that the developer's pure intent can actually shine through. 22 00:01:01.039 --> 00:01:03.799 And that brings me to this brilliant analogy I read 23 00:01:03.799 --> 00:01:08.040 recently about pianists, which perfectly sets up our mission today. 24 00:01:08.200 --> 00:01:11.560 It says, there are essentially different kinds of players. You know, 25 00:01:11.599 --> 00:01:13.719 You've got the ones who play just because they're forced too. 26 00:01:13.799 --> 00:01:16.000 Sure, they're reluctant students, right, and. 27 00:01:15.959 --> 00:01:18.519 Then you have the professionals who play beautifully just to 28 00:01:18.560 --> 00:01:23.040 get paid. But then there is this totally different breed 29 00:01:23.120 --> 00:01:26.439 of tinkerer. They aren't satisfied with just hearing the music. 30 00:01:26.519 --> 00:01:28.799 They want to physically take the piano apart. 31 00:01:28.879 --> 00:01:30.560 They want to see the mechanics, Yes. 32 00:01:30.840 --> 00:01:34.000 They want to understand the clever little escapements that lift 33 00:01:34.000 --> 00:01:36.560 the damper felt a fraction of a second before the 34 00:01:36.599 --> 00:01:38.200 hammers actually strike the strings. 35 00:01:38.799 --> 00:01:41.760 That is such a great visual And that metaphor was 36 00:01:41.760 --> 00:01:45.519 actually written by Eric Lippert in the forward to the 37 00:01:45.519 --> 00:01:49.040 incredible resource we are exploring today, which is see Sharp 38 00:01:49.079 --> 00:01:50.359 in Depth by John. 39 00:01:50.200 --> 00:01:53.280 Skeet, a truly legendary book in the programming world. 40 00:01:53.359 --> 00:01:57.560 Oh absolutely, and that pianist analogy captures exactly what we're 41 00:01:57.560 --> 00:01:59.640 about to do. We're not just learning how to play 42 00:01:59.640 --> 00:02:02.799 a few big chords today, We're taking the piano apart. 43 00:02:03.040 --> 00:02:06.000 Welcome to the deep dive. Today we are opening up 44 00:02:06.000 --> 00:02:08.599 the hood on c shark, which is, you know, one 45 00:02:08.639 --> 00:02:12.199 of the most widely used programming languages on Earth. It's everywhere, 46 00:02:12.280 --> 00:02:14.719 it really is. Whether you are listening to this on 47 00:02:14.759 --> 00:02:17.159 a podcast app or browsing a web store or playing 48 00:02:17.159 --> 00:02:20.319 a video game, c sharp is likely running somewhere behind 49 00:02:20.319 --> 00:02:23.599 the scenes. Our mission is to explore how this complex 50 00:02:23.719 --> 00:02:26.599 language evolved over time to become closer and closer to 51 00:02:26.719 --> 00:02:27.360 human thought. 52 00:02:27.599 --> 00:02:30.400 And you listening right now, you really don't need to 53 00:02:30.439 --> 00:02:32.680 be a software engineer to appreciate. 54 00:02:32.159 --> 00:02:35.240 This, not at all. If you have ever been frustrated 55 00:02:35.280 --> 00:02:37.800 by an app freezing on your phone, you're going to 56 00:02:37.840 --> 00:02:41.240 find out exactly why that happens and how modern systems 57 00:02:41.240 --> 00:02:42.240 are built to fix it. 58 00:02:42.439 --> 00:02:45.199 Because to truly understand the digital world you interact with 59 00:02:45.240 --> 00:02:47.479 every single day, you have to look at the tools 60 00:02:47.479 --> 00:02:49.560 you used to build it. A language like c sharp 61 00:02:49.680 --> 00:02:53.199 is it's basically a bridge. It connects the chaotic, messy 62 00:02:53.240 --> 00:02:57.199 reality of human ideas to the rigid, mathematical reality of 63 00:02:57.240 --> 00:02:58.520 a computer's processor. 64 00:02:58.960 --> 00:03:03.159 Okay, the War on Fluff, as we called it earlier. 65 00:03:03.520 --> 00:03:06.120 To appreciate how far things have come, we really need 66 00:03:06.159 --> 00:03:08.039 to go all the way back to c sharp version 67 00:03:08.039 --> 00:03:11.000 one and look at a classic everyday scenario. 68 00:03:11.120 --> 00:03:12.639 Sounds good. Where do we start. 69 00:03:12.879 --> 00:03:16.360 Let's say you are building an e commerce store. You 70 00:03:16.439 --> 00:03:18.759 have a product, say a pair of headphones. It has 71 00:03:18.800 --> 00:03:21.639 a name and it has a price. Now you want 72 00:03:21.680 --> 00:03:23.439 to put a bunch of these into a digital shopping 73 00:03:23.479 --> 00:03:26.240 cart in C sharp one. To create a list of 74 00:03:26.240 --> 00:03:29.000 those products, developers had to use a tool called an 75 00:03:29.080 --> 00:03:29.639 array list. 76 00:03:29.840 --> 00:03:33.840 Ah, yes, the infamous array list. And this is where 77 00:03:33.840 --> 00:03:36.319 the early limitations of the language you can very apparent. 78 00:03:36.520 --> 00:03:38.199 And a rayl liist is what we call a weekly 79 00:03:38.240 --> 00:03:38.960 typed collection. 80 00:03:39.120 --> 00:03:42.240 Weekly typed meaning it's not strict exactly. 81 00:03:41.800 --> 00:03:43.840 To the compiler, which you know, is the engine that 82 00:03:43.879 --> 00:03:46.719 translates your human metable code into the zeros and ones 83 00:03:46.879 --> 00:03:49.400 the machine actually understands. An arrayl list is just a 84 00:03:49.479 --> 00:03:51.560 dumb blind cardboard box. 85 00:03:51.759 --> 00:03:52.520 Blind box. 86 00:03:52.639 --> 00:03:55.560 Yeah, it knows that holmes things, but it has absolutely 87 00:03:55.599 --> 00:03:57.439 no idea what those things actually. 88 00:03:57.120 --> 00:04:00.840 Are, which I mean sounds kind of flexible at first, 89 00:04:00.879 --> 00:04:04.439 but think about the danger there. Because the compiler is blind. 90 00:04:05.080 --> 00:04:07.800 You could be filling your digital shopping cart with product 91 00:04:07.840 --> 00:04:11.319 objects and then a bug in your code accidentally shoves 92 00:04:11.360 --> 00:04:14.159 a random text string like the word banana into that 93 00:04:14.240 --> 00:04:15.520 exact same list. 94 00:04:15.360 --> 00:04:16.839 And the compiler wouldn't blink an. 95 00:04:16.720 --> 00:04:18.399 Eye right, it would just say, sure, put it in 96 00:04:18.399 --> 00:04:18.800 the box. 97 00:04:18.959 --> 00:04:22.079 And that creates a literal ticking time bomb in your 98 00:04:22.120 --> 00:04:25.439 software because there are two main phases in software development. 99 00:04:26.000 --> 00:04:28.720 You have compile time when you're building and checking the 100 00:04:28.759 --> 00:04:31.519 code on your machine, and then run time, when the 101 00:04:31.519 --> 00:04:33.800 code is actually executing out in the wild in the 102 00:04:33.839 --> 00:04:34.639 hands of the user. 103 00:04:34.759 --> 00:04:38.160 So the developer thinks everything is fine exactly if the 104 00:04:38.160 --> 00:04:41.600 compiler doesn't catch that mistake, the program compiles perfectly. 105 00:04:42.560 --> 00:04:45.439 But the moment you, the user try to check out, 106 00:04:45.800 --> 00:04:48.439 the program reaches into that box, pulls out the word 107 00:04:48.519 --> 00:04:51.879 banana instead of a product, realizes it doesn't have a price, 108 00:04:51.920 --> 00:04:53.360 and catastrophically crashes. 109 00:04:53.480 --> 00:04:56.600 The app freezes, the user is furious, and the sale 110 00:04:56.639 --> 00:04:58.920 is lost, all because the box was blind. 111 00:04:58.959 --> 00:05:00.160 It's a terrible user EXPERI. 112 00:05:00.560 --> 00:05:03.600 But then C sharp two comes along and introduces this 113 00:05:03.759 --> 00:05:07.759 massive structural shift called generics. Suddenly you don't just have 114 00:05:07.839 --> 00:05:10.800 a generic cardboard box anymore. You have a list of product. 115 00:05:11.279 --> 00:05:14.240 You are basically slapping a highly specific label on the 116 00:05:14.279 --> 00:05:16.959 outside of the box, explicitly telling it what it is 117 00:05:16.959 --> 00:05:17.680 allowed to hold. 118 00:05:17.959 --> 00:05:21.480 You were giving the compiler back its eyesight. By declaring 119 00:05:21.519 --> 00:05:24.279 a generic list of products. The compiler becomes a very 120 00:05:24.319 --> 00:05:25.160 strict inspector. 121 00:05:25.279 --> 00:05:26.839 It's checking at the door right. 122 00:05:27.240 --> 00:05:29.920 If a developer accidentally tries to insert a text string 123 00:05:29.920 --> 00:05:33.480 into that list, the compiler violently rejects it before the 124 00:05:33.519 --> 00:05:36.439 program is ever allowed to run. It forces the error 125 00:05:36.480 --> 00:05:39.160 to happen on the developer's laptop rather than on your 126 00:05:39.160 --> 00:05:41.000 smartphone while you were trying to buy. 127 00:05:40.839 --> 00:05:44.360 Something, moving the burden of checking from the user back 128 00:05:44.399 --> 00:05:47.160 to the system. I love that, But the removal of 129 00:05:47.199 --> 00:05:49.600 fluff really kicks into high gear with C SHAR three. 130 00:05:49.639 --> 00:05:51.839 Oh absolutely. C SHAR three was a game changer. 131 00:05:52.000 --> 00:05:55.279 Let's stick with our shopping card example. The user wants 132 00:05:55.319 --> 00:05:58.240 to sort those products by name. In the old days, 133 00:05:58.240 --> 00:06:00.839 you couldn't just say, you know, sort by name. You 134 00:06:00.920 --> 00:06:03.519 had to write an entirely separate block of code, a 135 00:06:03.560 --> 00:06:05.839 completely different class called an eye comparer. 136 00:06:06.160 --> 00:06:07.000 And it was painful. 137 00:06:07.279 --> 00:06:10.319 It was It was sometimes dozens of lines long, and 138 00:06:10.360 --> 00:06:13.959 its sole purpose was to explicitly define the mathematical mechanics 139 00:06:14.120 --> 00:06:16.000 of how to compare product A to product B. 140 00:06:16.480 --> 00:06:19.560 It was just exhausting boilerplate. You were totally bogged down 141 00:06:19.560 --> 00:06:23.279 in imperative programming, giving the computer step by step instructions 142 00:06:23.279 --> 00:06:26.120 on how to achieve a result, rather than simply stating 143 00:06:26.120 --> 00:06:27.040 what result you wanted. 144 00:06:27.279 --> 00:06:30.839 Enter C shar III and lambda expressions. We get this 145 00:06:31.160 --> 00:06:34.439 sleek little aerosyntax literally just an equal sign and a 146 00:06:34.480 --> 00:06:38.519 greater than sign, and that massive, clunky block of comparison 147 00:06:38.560 --> 00:06:42.680 code shrinks down into a single, beautiful one liner, just dot. 148 00:06:42.519 --> 00:06:44.680 Order by parop dot do. 149 00:06:45.000 --> 00:06:48.360 Name yes, which brings me back to the contractor analogy. 150 00:06:48.720 --> 00:06:51.240 We finally stopped telling the contractor how to swing the hammer. 151 00:06:51.240 --> 00:06:52.839 We just handed them a picture of the finished house 152 00:06:52.839 --> 00:06:54.040 and said build that. 153 00:06:54.040 --> 00:06:57.839 That transition from imperative to declarative programming is arguably the 154 00:06:57.839 --> 00:07:00.360 most profound shift in the history of C shark, and 155 00:07:00.399 --> 00:07:03.399 the absolute pinnacle of that shift in C sharp III is. 156 00:07:03.519 --> 00:07:07.279 Li INQ, which stands for Language Integrated Query Correct. 157 00:07:07.720 --> 00:07:12.040 LIANQ allows developers to filter and sort data using a clean, 158 00:07:12.240 --> 00:07:15.680 incredibly readable syntax that looks a lot like SQL, which 159 00:07:15.720 --> 00:07:17.360 is a language used for databases. 160 00:07:17.800 --> 00:07:20.600 So instead of writing nested loops like look at every item, 161 00:07:20.639 --> 00:07:22.879 if it matches this condition, put it in a new pile, 162 00:07:22.920 --> 00:07:26.120 then sort that pile. You just write one sentence, select 163 00:07:26.120 --> 00:07:28.600 products where price is under twenty dollars, order. 164 00:07:28.439 --> 00:07:31.879 By name exactly. And the real magic is that lanq 165 00:07:32.319 --> 00:07:35.839 works identically whether you are querying data sitting in your 166 00:07:35.839 --> 00:07:40.120 computer's active memory, a text file, or a massive external database. 167 00:07:40.279 --> 00:07:41.639 It abstracts all that away. 168 00:07:41.759 --> 00:07:44.160 It does you express the pure intent of your question, 169 00:07:44.680 --> 00:07:47.839 and the compiler orchestrates the complex machinery required to fetch 170 00:07:47.879 --> 00:07:48.319 the answer. 171 00:07:48.639 --> 00:07:51.879 Okay, making code elegant in a pristine environment is great, 172 00:07:52.160 --> 00:07:54.560 but anyone who has ever used a computer knows the 173 00:07:54.600 --> 00:07:56.720 real world is incredibly messy. 174 00:07:56.759 --> 00:07:57.560 Oh it's chaotic. 175 00:07:57.920 --> 00:08:02.079 Data is chaotic, it's missing, or it belongs to legacy 176 00:08:02.120 --> 00:08:06.160 systems that stubbornly refuse to speak our modern language. So 177 00:08:06.199 --> 00:08:10.120 how did c sharp adapt to the chaos. Let's take 178 00:08:10.120 --> 00:08:13.600 the problem of missing data back to our e commerce store. 179 00:08:13.759 --> 00:08:16.120 Imagine we have a brand new product that is listed 180 00:08:16.120 --> 00:08:18.959 in the catalog, but the marketing team hasn't finalized the 181 00:08:19.000 --> 00:08:21.680 price yet. We literally do not know the price. 182 00:08:22.319 --> 00:08:26.000 This simple reality caused massive headaches in early versions of 183 00:08:26.040 --> 00:08:29.560 c sharp. A price is typically represented as a decimal. 184 00:08:29.839 --> 00:08:32.000 A decimal is what we call a value type, a 185 00:08:32.039 --> 00:08:34.360 concept we will explore deeply in just a few minutes. 186 00:08:34.840 --> 00:08:37.360 But the crucial limitation of a value type in C 187 00:08:37.519 --> 00:08:40.440 sharp one was that it could not naturally be empty. 188 00:08:40.519 --> 00:08:43.200 It was a solid block of memory that absolutely had 189 00:08:43.240 --> 00:08:45.639 to contain a number by default. If you didn't give 190 00:08:45.639 --> 00:08:47.360 it one, it defaulted to zero. 191 00:08:47.480 --> 00:08:49.279 And if you are a store owner, zero is the 192 00:08:49.279 --> 00:08:50.759 most dangerous possible price. 193 00:08:50.879 --> 00:08:51.679 It's a disaster. 194 00:08:51.960 --> 00:08:54.480 If you default an unknown price to zero, users will 195 00:08:54.480 --> 00:08:56.279 immediately add it to their cart and try to check 196 00:08:56.279 --> 00:08:57.919 out for free. You simply can't allow that. 197 00:08:58.159 --> 00:09:01.320 So developers were forced to end near these terrible hacks. 198 00:09:01.919 --> 00:09:05.279 They would create a boolean flag, literally, a completely separate, 199 00:09:05.559 --> 00:09:09.399 disconnected true or false variable named something like sprice vallat, 200 00:09:09.919 --> 00:09:10.600 just hanging. 201 00:09:10.399 --> 00:09:12.320 Around to tell the program whether or not to trust 202 00:09:12.320 --> 00:09:13.759 the decimal number exactly. 203 00:09:14.360 --> 00:09:16.679 Or worse, they would use a magic number. They'd set 204 00:09:16.679 --> 00:09:19.840 the price to negative one million, trusting that no real 205 00:09:19.879 --> 00:09:23.320 product would ever cost that, just to represent the unknown state. 206 00:09:23.679 --> 00:09:26.720 Imagine trying to maintain a database where half the columns 207 00:09:26.759 --> 00:09:30.080 are just secondary flags, trying to explain if the primary 208 00:09:30.080 --> 00:09:33.879 columns are actually real. It's a nightmare. But then C 209 00:09:34.120 --> 00:09:37.840 sharp two brings in nullible types, and the syntax is 210 00:09:37.919 --> 00:09:39.480 almost shockingly simple. 211 00:09:39.759 --> 00:09:41.679 What's fascinating here is that they solved it with a 212 00:09:41.720 --> 00:09:44.120 single character. You just add a question mark to the 213 00:09:44.159 --> 00:09:46.679 type declaration. So decimal question mark price. 214 00:09:46.720 --> 00:09:48.799 That's a question mark, and it changes everything. 215 00:09:48.919 --> 00:09:52.000 It entirely changes the semantic meaning of the concept of null. 216 00:09:52.600 --> 00:09:55.600 Previously null just meant a missing reference, a dead end. 217 00:09:56.080 --> 00:10:00.000 With nullible types, null explicitly models the absence of days. 218 00:10:00.399 --> 00:10:01.679 It's a legitimate state now. 219 00:10:01.960 --> 00:10:05.600 Yes, it allows the language to gracefully handle the messy 220 00:10:05.639 --> 00:10:10.000 reality that sometimes I don't know is the only accurate answer. 221 00:10:10.200 --> 00:10:14.759 It models reality beautifully. But speaking of reality, sometimes your 222 00:10:14.879 --> 00:10:18.120 modern elegant C sharp code has to talk to the 223 00:10:18.159 --> 00:10:19.879 ghosts of Microsoft past. 224 00:10:20.120 --> 00:10:22.639 Ah. Yes, legacy systems. 225 00:10:22.679 --> 00:10:26.799 I'm talking about legacy comm technologies, the old underlying machinery 226 00:10:26.960 --> 00:10:30.919 used to automate things like Microsoft Excel or Word. In 227 00:10:30.960 --> 00:10:33.759 the old days, talking to those systems was brutal because 228 00:10:33.799 --> 00:10:37.480 their method signatures, you know, the strict contract of inputs 229 00:10:37.480 --> 00:10:41.600 a piece of code. Demands would sometimes require fifteen different variables. 230 00:10:41.679 --> 00:10:43.799 Even if you only wanted to open a file and 231 00:10:43.879 --> 00:10:46.519 you only cared about the file name, the legacy system 232 00:10:46.559 --> 00:10:49.200 still forced you to pass in fourteen other dummy values 233 00:10:49.480 --> 00:10:50.799 just to satisfy the contract. 234 00:10:50.879 --> 00:10:54.720 But C sharfour introduces named arguments and optional parameters. You 235 00:10:54.840 --> 00:10:57.240 just name the one piece of data you actually care about, 236 00:10:57.279 --> 00:11:00.000 pass it in, and the compiler quietly fills in all 237 00:11:00.039 --> 00:11:03.159 all the other blank spaces with default values behind the scenes. 238 00:11:03.200 --> 00:11:05.799 It's a huge quality of life improvement, it really is. 239 00:11:06.440 --> 00:11:08.440 But wait, I want to pause and push back on 240 00:11:08.480 --> 00:11:11.240 something from C sharfour because it sounds like a massive 241 00:11:11.240 --> 00:11:13.519 contradiction to everything we've established so far. 242 00:11:13.720 --> 00:11:14.159 Let's hear it. 243 00:11:14.600 --> 00:11:17.320 We spent the first half of this deep dive praising 244 00:11:17.360 --> 00:11:20.919 the compiler for being a strict inspector. C sharp is 245 00:11:20.960 --> 00:11:24.279 famously a statically typed language. The compiler wants to know 246 00:11:24.360 --> 00:11:27.279 exactly what every variable is before the code is ever 247 00:11:27.360 --> 00:11:29.559 allowed to run, which is what keeps us safe. Sure, 248 00:11:29.759 --> 00:11:33.639 but C scharfur introduced the dynamic keyword. It lets you 249 00:11:33.679 --> 00:11:36.440 write code where the right piler basically turns off, shrugs 250 00:11:36.480 --> 00:11:38.720 its shoulders, and says, I have no idea what this is, 251 00:11:38.759 --> 00:11:42.639 I'll figure it out later. Isn't that breaking the fundamental 252 00:11:42.720 --> 00:11:44.039 sacred rule of the language. 253 00:11:44.080 --> 00:11:47.080 It looks exactly like a contradiction on the surface, but 254 00:11:47.159 --> 00:11:51.000 it is actually a profound demonstration of pragmatic design. C 255 00:11:51.200 --> 00:11:55.840 sharp remains overwhelmingly statically typed, but there are specific, isolated 256 00:11:55.879 --> 00:11:59.480 scenarios where you absolutely must talk to environments that don't 257 00:11:59.480 --> 00:12:02.759 play by those rules, like Python scripts or very flexible 258 00:12:02.759 --> 00:12:03.799 web services. 259 00:12:03.480 --> 00:12:06.279 Because Python is a dynamic language where variables can change 260 00:12:06.279 --> 00:12:07.159 their pipe on the fly. 261 00:12:07.480 --> 00:12:11.679 Correct If c shark rigidly refuse to bend its rules, 262 00:12:12.200 --> 00:12:15.200 developers trying to bridge those two worlds would be forced 263 00:12:15.200 --> 00:12:18.480 to use something called reflection, and reflection is bad well. 264 00:12:18.519 --> 00:12:21.679 Reflection is a highly complex process where a program has 265 00:12:21.679 --> 00:12:24.440 to blindly examine itself or another program while it's running 266 00:12:24.639 --> 00:12:27.519 without a map. It's like trying to navigate a dark 267 00:12:27.600 --> 00:12:30.519 room by just walking forward until you bump into the furniture. 268 00:12:31.120 --> 00:12:34.919 It is slow for both and incredibly error prone. 269 00:12:35.000 --> 00:12:38.000 So the dynamic keyword is like handing the developer a 270 00:12:38.080 --> 00:12:40.159 specialized flashlight for that dark room. 271 00:12:40.360 --> 00:12:44.519 Yes, exactly. By introducing dynamic sea sharp lets you selectively 272 00:12:44.559 --> 00:12:47.919 bypass the compiler strict checks, but only when you explicitly 273 00:12:47.919 --> 00:12:51.320 declare that you need to. It sacrifices a tiny sliver 274 00:12:51.360 --> 00:12:54.279 of theoretical purity to give the developer a massive amount 275 00:12:54.320 --> 00:12:55.440 of practical capability. 276 00:12:55.519 --> 00:12:57.320 I will let you break the rules, but you have 277 00:12:57.360 --> 00:12:58.480 to sign a waiver first. 278 00:12:58.639 --> 00:12:59.519 That's a great way to put it. 279 00:12:59.559 --> 00:13:03.519 That makes makes sense. Okay, we've tackled data and legacy systems, 280 00:13:03.840 --> 00:13:05.919 but if we look at modern applications, the ones you 281 00:13:05.960 --> 00:13:08.279 and I use every day on our phones and laptops, 282 00:13:08.759 --> 00:13:13.440 the biggest bottleneck isn't usually calculating data. It's waiting for it. 283 00:13:13.720 --> 00:13:19.320 Oh. Absolutely, network latency, downloading images, querying a database sitting 284 00:13:19.360 --> 00:13:21.200 on a server halfway across the world. 285 00:13:21.399 --> 00:13:24.480 Right, think about your own experience listening to this. If 286 00:13:24.559 --> 00:13:28.200 your podcast app needs to download the next episode and 287 00:13:28.279 --> 00:13:32.360 the entire screen completely freezes and becomes unresponsive while it 288 00:13:32.440 --> 00:13:35.279 waits for that file, that is a terrible user experience. 289 00:13:35.519 --> 00:13:36.519 You probably delete the. 290 00:13:36.519 --> 00:13:37.480 App without a doubt. 291 00:13:37.679 --> 00:13:40.759 And solving that freezing problem brings us to the absolute 292 00:13:41.000 --> 00:13:44.320 crown jewel of CSHAR five async and a weight. 293 00:13:44.759 --> 00:13:47.559 To really appreciate the elegance of asinc and a weight, 294 00:13:47.639 --> 00:13:52.039 you must understand the historical trauma of asynchronous programming before 295 00:13:52.120 --> 00:13:55.399 CSHAR five. To prevent that screen from freezing, you had 296 00:13:55.440 --> 00:13:57.480 to take the downloading task and push it onto a 297 00:13:57.519 --> 00:14:00.759 background thread, a completely separate track of act execution. Makes 298 00:14:00.799 --> 00:14:03.559 sense so far, but there's an ironclad golden rule in 299 00:14:03.639 --> 00:14:07.639 software development. A background thread is never ever allowed to 300 00:14:07.679 --> 00:14:09.360 directly update the user interface. 301 00:14:09.480 --> 00:14:12.320 Wait really, so if the background thread finishes the download 302 00:14:12.360 --> 00:14:14.519 and tries to directly update the text on a button 303 00:14:14.559 --> 00:14:16.399 to say complete, what happens? 304 00:14:16.440 --> 00:14:19.600 The entire application crashes violently. Oh wow, yeah, because the 305 00:14:19.639 --> 00:14:23.080 main UI thread aggressively protects its domain. So to get 306 00:14:23.120 --> 00:14:26.159 around this, developers wrote what is universally known as. 307 00:14:26.120 --> 00:14:28.000 Spaghetti code, Everyone's favorite. 308 00:14:28.080 --> 00:14:30.639 You start the download on track A, then you write 309 00:14:30.639 --> 00:14:34.120 a complex callback function that just sits and waits. When 310 00:14:34.120 --> 00:14:37.960 the data arrives, that callback has to carefully package the 311 00:14:38.039 --> 00:14:41.480 data up and marshal it back across the boundary to 312 00:14:41.559 --> 00:14:42.840 the main UI thread. 313 00:14:43.039 --> 00:14:45.399 It's like reading a Choose your Own Adventure book where 314 00:14:45.480 --> 00:14:48.480 every single page forces you to jump to three different 315 00:14:48.559 --> 00:14:51.159 chapters just to finish one cohesive sentence. 316 00:14:51.200 --> 00:14:52.720 That's exactly how it felt. 317 00:14:52.559 --> 00:14:56.720 Your Logit is completely fractured. Standard error handling like trcatch 318 00:14:56.759 --> 00:15:00.440 blocks completely breaks down because the code is constantly jumping 319 00:15:00.480 --> 00:15:02.200 across different execution tracks. 320 00:15:02.320 --> 00:15:03.440 It was a mess. Todybug. 321 00:15:03.679 --> 00:15:06.720 Here's where it gets really interesting. With asinc and a weight, 322 00:15:07.080 --> 00:15:09.360 you write your code exactly like you used to in 323 00:15:09.399 --> 00:15:11.759 the simple days. It reads top to bottom, line one, 324 00:15:11.840 --> 00:15:16.320 line two, line three. Your error handling wraps around it perfectly. 325 00:15:16.559 --> 00:15:18.320 It reads synchronously, right. 326 00:15:18.960 --> 00:15:21.399 But I have to ask, how if I type the 327 00:15:21.399 --> 00:15:24.320 word a weight before a download, is the compiler just 328 00:15:24.399 --> 00:15:27.440 quietly spinning up a bunch of new background threads behind 329 00:15:27.440 --> 00:15:29.840 the scenes to hide the messy choose your own adventure 330 00:15:29.879 --> 00:15:30.519 logic from me. 331 00:15:31.200 --> 00:15:34.720 That is the most common and persistent misconception, and it 332 00:15:34.759 --> 00:15:37.120 is vital we clear it up. Hmmm, No, it is 333 00:15:37.159 --> 00:15:39.360 not necessarily spinning up new threads at all. 334 00:15:39.480 --> 00:15:41.639 It's not. Then how does the screen not. 335 00:15:41.720 --> 00:15:45.559 Freeze through an awe inspiring compiler transformation known as the 336 00:15:45.600 --> 00:15:49.159 state machine. When you use the awight keyword, you are 337 00:15:49.159 --> 00:15:53.480 telling the compiler to pause the execution of that specific method. 338 00:15:53.639 --> 00:15:56.679 The compiler takes your method, chops it up, and completely 339 00:15:56.679 --> 00:15:57.960 rewrites it behind the scenes. 340 00:15:58.279 --> 00:15:59.559 What does that actually look like? 341 00:15:59.639 --> 00:16:02.159 In PRAC Think of it like reading a thick novel 342 00:16:02.240 --> 00:16:04.440 and suddenly you need to go cook dinner. You don't 343 00:16:04.480 --> 00:16:06.519 just stare at the page until dinner is done. You 344 00:16:06.559 --> 00:16:09.120 take a sticky note, write down exactly what page you're on, 345 00:16:09.200 --> 00:16:11.399 what line you were reading, and what the characters were 346 00:16:11.440 --> 00:16:11.799 just doing. 347 00:16:12.080 --> 00:16:13.000 You mark your place. 348 00:16:13.360 --> 00:16:16.279 Yes, you place a sticky note in the book, close 349 00:16:16.320 --> 00:16:17.879 it and walk away to do something else. 350 00:16:17.960 --> 00:16:19.799 You yield your attention exactly. 351 00:16:20.240 --> 00:16:23.679 The awake keyword leaves a digital sticky note. It captures 352 00:16:23.679 --> 00:16:26.080 the exact state of all your local variables and the 353 00:16:26.080 --> 00:16:32.159 synchronization context. Then it gracefully exits the method, instantly returning 354 00:16:32.200 --> 00:16:33.679 control to the main UI thread. 355 00:16:33.879 --> 00:16:35.360 So the UI thread is free again. 356 00:16:35.519 --> 00:16:38.279 Right. That thread is now entirely free to handle the 357 00:16:38.360 --> 00:16:40.399 users scrolling, clicking, and interacting. 358 00:16:40.840 --> 00:16:44.080 The screen never freezes, but the DOWNLA is still happening 359 00:16:44.080 --> 00:16:44.720 somewhere right. 360 00:16:44.840 --> 00:16:48.159 Yes, usually hand it off to the operating system's network drivers. 361 00:16:48.600 --> 00:16:50.799 And when those drivers tap the program on the shoulder 362 00:16:50.840 --> 00:16:54.080 and say, hey, the date is here, the state machine 363 00:16:54.120 --> 00:16:56.519 looks at its sticky note, jumps right back to the 364 00:16:56.559 --> 00:16:59.000 exact line of code it left off at, restores all 365 00:16:59.039 --> 00:17:01.279 the variables, and continues reading the book as if it 366 00:17:01.320 --> 00:17:01.840 never left. 367 00:17:02.200 --> 00:17:05.200 That is mind blowing. The compiler absorbs all the complexity 368 00:17:05.240 --> 00:17:07.599 of the state machine. So my intent wait for this 369 00:17:07.680 --> 00:17:10.400 to finish, then do the next thing reads as cleanly 370 00:17:10.440 --> 00:17:11.160 as English. 371 00:17:11.200 --> 00:17:12.440 It's beautiful engineering. 372 00:17:12.599 --> 00:17:15.240 Okay, but we need to pivot because we've been talking 373 00:17:15.279 --> 00:17:18.799 about all this magic state machines leaving sticky notes, L 374 00:17:19.000 --> 00:17:23.200 and Q, querying databases, lambda's sorting lists. None of this 375 00:17:23.279 --> 00:17:26.680 floats in a vacuum. How does the language actually package 376 00:17:26.720 --> 00:17:28.920 up that sticky note to execute it later. 377 00:17:29.039 --> 00:17:31.039 We have to look at the foundations right. 378 00:17:31.160 --> 00:17:33.519 To truly appreciate the magic. We have to look at 379 00:17:33.519 --> 00:17:35.599 the engine that has been hiding in the car since 380 00:17:35.680 --> 00:17:40.440 day one, the core machinery, delegates and the type system, and. 381 00:17:40.400 --> 00:17:43.519 Those two concepts are at the absolute bedrock upon which 382 00:17:43.559 --> 00:17:44.920 all the modern features are built. 383 00:17:45.079 --> 00:17:48.000 Let's start with delegates. Think about how a last will 384 00:17:48.039 --> 00:17:51.000 and testament works in the real world. You are sitting 385 00:17:51.039 --> 00:17:55.319 in an office today writing down specific instructions sell this asset, 386 00:17:55.519 --> 00:17:58.720 donate this money to charity. But those instructions don't. 387 00:17:58.519 --> 00:18:00.559 Happen right now, right they happen in the future. 388 00:18:00.640 --> 00:18:03.200 You are packaging them up, handing them to an attorney, 389 00:18:03.240 --> 00:18:07.200 and saying, execute these instructions later under specific conditions. 390 00:18:07.400 --> 00:18:10.000 A delegate and see start operates exactly like that will. 391 00:18:10.279 --> 00:18:13.279 It is a secure container for an action you are 392 00:18:13.359 --> 00:18:16.519 encapsulating a method, a set of instructions, and handing it 393 00:18:16.559 --> 00:18:18.759 off to another part of your application. 394 00:18:18.480 --> 00:18:19.759 So it's portable logic. 395 00:18:19.960 --> 00:18:23.880 Exactly, you are saying, when the user clicks this button 396 00:18:24.079 --> 00:18:28.279 or when the network download finishes, execute this delegate. It 397 00:18:28.359 --> 00:18:32.440 is the exact mechanism that powers the acing state machines 398 00:18:32.480 --> 00:18:33.319 we just discussed. 399 00:18:33.559 --> 00:18:36.519 And a delegate doesn't just hold one instruction. It holds 400 00:18:36.519 --> 00:18:40.359 an invitation list. You can stack multiple actions inside it, 401 00:18:40.599 --> 00:18:42.839