ASP.NET Core web apps with EF Core

- Hi, I'm Cam Soper, I'm a content developer working on .NET Docs here at Microsoft, and welcome back to Entity Framework Core 101. In this video, I'm going to show you how you can use Entity Framework Core with ASP.NET Core scaffolding to streamline your web development. You can see in Visual Studio, I've got a mostly empty web application. This web application already has ContosoPetsContext DbContext, as well as an entity model. The entity model reflects a working database that's already running in production. The first thing I'm going to do is I'm going to register our ContosoPetsContext with ASP.NET Core's dependency injection container. The way I do this is by calling AddDbContext on the services class in ConfigureServices in the startup.cs. You'll note that we're passing in UseSqlServer on the options, along with our connection string. And again, please don't ever hard-code your connection strings. We're going to use the scaffold to generate Razor pages to support adding, editing, deleting, and reading products. I've created a Products folder. And on that folder, I'm going to right-click, go to Add, Razor Pages, and Razor Pages using Entity Framework CRUD. I'll select Product as the model class and ContosoPetsContext as the data context class. Visual Studio creates five pages, Create, Delete, Details, Edit, and Index. If we run the application, we can look at the Index page, which lists the products. Let's look at the code behind this Index page. If we look at the constructor for the PageModel behind the Index page, you'll note that we're injecting ContosoPetsContext into the constructor. ASP.NET Core's dependency injection container takes care of this for us. All we have to do is make a constructor with the right signature. The product itself, the list of products rather, is contained on a property on the PageModel class. The view enumerates over that list of products and for each product, lists the name and price. Let's create a new product. So there's our new product. Let's look at what happened in the code. We'll start with the PageModel. The OnGet method in the PageModel returns the empty form, which is a Razor view. The Razor view has elements to support name and price. We have label, input, and span that combine to form the form that we saw earlier, including validation that enforces the constraints in our entity model. When we post the form, the model binder binds the elements on the form to our product property, which we then add to our products table and SaveChangesAsync. Let's edit an entity. Note that on this form, the name and price elements were pre-populated with the existing data before we changed it. If we look at the PageModel for Edit, on the OnGet, we're querying our database context for products that match the ID that was passed in on the URL's query string. We retrieve that product and present it for the user to edit. Now, when the user posts the form, the model binder grabs that same product object and attaches it to the database context, finds the existing product, marks it as modified, and saves the changes. The final operation we're going to look at is the Delete. The Delete form is actually kind of similar to the Edit form. The very first thing we do on OnGet is we look up the product by ID and display it for the user. When the user clicks the Submit button, which posts, we find that same product by its ID, we call Remove on the products table passing in that entity, and we save our changes. In this video, we looked at how easy it is to use the ASP.NET Core scaffolding along with Entity Framework to streamline your web development. In the next video, we're going to look at using different database providers with Entity Framework Core.