WEBVTT 00:00.020 --> 00:00.320 Okay. 00:00.320 --> 00:03.500 In this lesson we're going to create our first class. 00:03.590 --> 00:04.820 We're going to create our own. 00:04.850 --> 00:08.090 Well start creating our own code for our own application. 00:08.090 --> 00:12.800 And the way that we're going to start this is we're going to create a class. 00:12.860 --> 00:18.530 And the type of class we're going to create is often referred to as an entity class, as we're going 00:18.560 --> 00:26.660 to be using this class with a framework called Entity Framework, which we're going to introduce shortly. 00:26.660 --> 00:32.990 So they're often referred to as entities even though they're just typical C-sharp classes. 00:33.020 --> 00:38.150 And when you start a new project or you're sat in front of your computer thinking, right, I'm going 00:38.180 --> 00:42.530 to create this thing, it's quite common to ask, where do I begin? 00:42.530 --> 00:47.870 And the answer often lies in the type of application you're building and what its purpose is. 00:47.900 --> 00:52.580 Well, we're creating an e-commerce store and we're going to be selling products. 00:52.580 --> 00:57.650 The type of product doesn't matter, but it's going to be a ski shop, so it's going to be ski related 00:57.650 --> 00:58.550 products. 00:58.550 --> 01:06.450 And a good starting point for this type of application is going to be to create a class that will hold 01:06.450 --> 01:08.880 properties applicable to a product. 01:08.880 --> 01:16.290 So inside the API folder we'll create a new folder and we will call it entities. 01:16.920 --> 01:19.770 And did I spell that correctly. 01:19.800 --> 01:20.850 Yes I did. 01:20.880 --> 01:22.860 Okay so let's create a new file. 01:22.860 --> 01:25.380 And this is going to be called products. 01:25.380 --> 01:28.440 And when I say create a new file I did that quite quickly. 01:28.440 --> 01:34.590 But inside the solution explorer if we create a new file then we're given a list of different templates 01:34.590 --> 01:37.590 that we can create a C sharp object from. 01:37.590 --> 01:40.080 Now we're interested in creating a class. 01:40.080 --> 01:41.610 So we'll select class. 01:41.610 --> 01:45.600 And then the name of the class is going to be called product. 01:46.170 --> 01:53.610 And when we create the class this way using Solution Explorer and right click the folder and say new 01:53.610 --> 01:54.270 file. 01:54.300 --> 01:55.800 Then we get the template. 01:55.800 --> 02:01.350 And what this gives us is the boilerplate that we need for a typical C sharp class. 02:01.350 --> 02:03.200 Now a couple of things to highlight here. 02:03.200 --> 02:09.650 We've got this using system, but it's kind of grayed out because it's not being used inside this class. 02:10.190 --> 02:11.240 And do we need it. 02:11.270 --> 02:13.850 Well no we can actually remove this. 02:13.850 --> 02:16.160 So we can remove using system. 02:16.160 --> 02:18.260 And we've also got a namespace. 02:18.260 --> 02:21.050 Now this is a logical location. 02:21.620 --> 02:26.870 When we create this it matches the physical name of the folder that we created it in. 02:26.870 --> 02:28.490 But it doesn't have to be that way. 02:28.490 --> 02:30.230 It's a logical namespace. 02:30.650 --> 02:36.710 But what this effectively means is I could create a class called product inside the controllers, let's 02:36.710 --> 02:45.800 say namespace, and it wouldn't conflict with a class with the same name that's located in the entities 02:46.100 --> 02:48.920 or API entities namespace. 02:49.220 --> 02:53.360 So each class we create is going to have a namespace where it logically resides. 02:53.360 --> 02:59.000 And this provides or this prevents us from having conflicts with classes that are in the same name. 02:59.000 --> 03:05.000 Not a big deal in our own small project such as it is, but as we introduce other packages, we'll be 03:05.000 --> 03:08.270 using classes from other packages that we add to our project. 03:08.720 --> 03:12.110 Then there may be a conflict if we don't have this namespace system. 03:12.110 --> 03:16.910 So let's go ahead and create some properties for a product. 03:16.910 --> 03:20.690 And we have snippets that come with the dev kit. 03:20.690 --> 03:24.590 And if I start typing prop and press return. 03:24.680 --> 03:30.320 And this type of property is called an auto implemented property. 03:30.320 --> 03:36.590 And when we create a property in this way, then the C-sharp compiler automatically generates a private 03:36.590 --> 03:40.250 backing field behind the scenes to store the property value. 03:40.250 --> 03:42.410 Another way of creating a property. 03:42.410 --> 03:47.810 If I do the full version, then prop full is the property and backing field. 03:47.810 --> 03:53.750 So we have a private variable and then the name of the property, and we have a getter and setter. 03:53.750 --> 04:01.310 But using the auto implemented property, we get all of that in a single line with a getter and setter. 04:01.340 --> 04:06.560 Now we need this to be public because this is going to be accessed by Entity Framework, and Entity 04:06.590 --> 04:10.430 Framework will need access to get and set properties. 04:10.490 --> 04:14.840 And the first property that we'll create is going to be an ID property. 04:15.050 --> 04:19.460 Now when it comes to Entity Framework that we're going to introduce soon, then we're going to talk 04:19.460 --> 04:20.900 about conventions. 04:20.930 --> 04:28.790 And one convention for Entity Framework is if we call a property ID, then it's going to use that property 04:28.790 --> 04:33.110 as the primary key for our database table when it creates it. 04:33.410 --> 04:35.780 We're also going to have a property for the name of the product. 04:35.780 --> 04:38.750 So that's going to be a string and we'll call it name. 04:38.750 --> 04:42.980 I'm going to ignore warnings just while I populate the different properties that we need and come back 04:43.010 --> 04:43.550 to them. 04:43.610 --> 04:49.070 We're going to have another one called description for the description of the product. 04:49.070 --> 04:52.070 And we'll also have a price. 04:52.100 --> 04:56.750 Now, it might be tempting to use the decimal here, but for a very specific reason. 04:56.990 --> 05:01.880 And the very specific reason is the payment provider that we're going to be using later on. 05:01.880 --> 05:09.200 They use long for the a currency value and we'll just stick to using the same, which saves us converting 05:09.200 --> 05:10.040 it later. 05:10.040 --> 05:16.310 And it just means that we'll need to divide everything by 100 in order to get the decimal value. 05:16.310 --> 05:23.630 And we'll also have another property for the string of the picture you URL of the product. 05:23.630 --> 05:27.890 Another reason for using long, by the way, is we don't need to worry about accuracy. 05:28.370 --> 05:36.440 When we use that as a decimal, we'll need to define the number of decimal places that we'll allow for 05:36.440 --> 05:40.490 accuracy, where as long we don't need to worry about that either. 05:40.490 --> 05:41.900 So we've got the picture URL. 05:41.900 --> 05:43.190 We'll have another few properties. 05:43.190 --> 05:48.950 We're going to have a string for the type of the product, and we'll have a string for the brand of 05:48.950 --> 05:49.700 the product. 05:49.700 --> 05:51.260 And one more property. 05:51.290 --> 05:56.930 We'll just have an int for the quantity in stock. 05:56.930 --> 05:59.060 So that will be enough to get us started. 05:59.060 --> 06:00.140 But we've got some warnings. 06:00.140 --> 06:05.960 And these warnings are related to the nullable reference types that we mentioned briefly earlier on. 06:05.990 --> 06:12.440 Now it's telling us that because we've got this nullable flag enabled, then we need to ensure we either 06:12.440 --> 06:16.940 make this property name optional, as in it's not going to be required. 06:16.940 --> 06:25.040 So our compiler knows that if we try and use the name somewhere or we don't check for its existence, 06:25.040 --> 06:30.200 then it's going to stop us from doing so because we'll run into a problem if we try and access something 06:30.200 --> 06:32.090 or use something that is null. 06:32.120 --> 06:33.080 But we don't want that. 06:33.080 --> 06:36.740 We want our products to have names, so we don't want to make this optional. 06:37.040 --> 06:39.230 Another approach to this is to initialize the value. 06:39.260 --> 06:45.500 We could initialize the name to an empty string, but then that would also not be great because now 06:45.500 --> 06:50.090 we could have properties with empty strings in our database, or products with empty string names in 06:50.090 --> 06:50.690 our database. 06:50.690 --> 06:52.100 We don't want that either. 06:52.550 --> 06:56.120 But since C-sharp seven we have a required modifier. 06:56.120 --> 07:02.450 And what this required modifier means that when we create a new product, a new instance of a product, 07:02.930 --> 07:08.630 then we are required to supply it when we initialize that product with a name property. 07:08.660 --> 07:11.420 And that's the approach we will take here. 07:11.420 --> 07:15.710 So we're going to give all of these string values the required modifier. 07:16.220 --> 07:18.740 And we'll do the same for the picked URL. 07:18.890 --> 07:27.830 And the type accidentally clicked on references there and for the brand as well. 07:27.860 --> 07:31.940 Now we don't need to do that for the quantity in stock or the price. 07:31.940 --> 07:39.140 And the reason for that is if I create a new product and I do not initialize the price or the quantity, 07:39.530 --> 07:42.680 then that's going to give it the default value for that type. 07:42.800 --> 07:47.330 And in the case of long that's going to be zero the int it would be zero. 07:47.360 --> 07:50.930 So it's always going to have a value even if it's the default value. 07:50.930 --> 07:55.190 But what it will not be is null because it's not a reference type. 07:55.190 --> 07:56.780 It's a value type. 07:57.320 --> 07:59.330 So that's our entity created. 07:59.330 --> 08:03.620 And how we use entities is we're going to take a look at Entity Framework. 08:03.620 --> 08:06.920 And we're going to introduce that next.