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Databases with Entity Framework

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Contents

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Entity Framework (EF)

  • This lecture will assume you have a basic understanding of SQL databases @@ -42,7 +41,7 @@
  • Allows creation of CRUD operations without writing SQL
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Entity Framework Core (EF Core)

  • EF Core is a cross-platform version of EF
    • @@ -52,7 +51,7 @@
  • This is what we'll be using
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Code First vs Database First vs Model First

  • There are three approaches through which Entity Framework can be implemented @@ -65,7 +64,7 @@
  • Database First and Code First are the most used ones and will be introduced in this lecture
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Note about loading data

  • In EF Core, you can use navigation properties in your model to load related entities
    • @@ -78,10 +77,10 @@
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Code First approach

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Code First

  • In the Code First approach, Entity Framework will create databases and tables based on defined entity classes
    • @@ -101,7 +100,7 @@
  • Not preferred for data intensive applications
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Required Packages

  • Install and add the following packages to your project: @@ -116,7 +115,7 @@

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Code First: DbContext

  • Let's begin with the Code First Approach
    • @@ -131,7 +130,7 @@ b) classes to keep the database up-to-date with CRUD operations
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Creating a context

  • Create a context that inherits from DbContext @@ -151,7 +150,7 @@ b) classes to keep the database up-to-date with CRUD operations
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  • To further configure how the database will be structured, override the OnModelCreating method
  • In this example, one table named Contact with columns Id, Name and Email will be created:
    public class ContactsContext : DbContext
@@ -168,7 +167,7 @@ b) classes to keep the database up-to-date with CRUD operations
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  • In this example, the Contact table will be created with some starting values for Id, Name and Email columns:
    public class ContactsContext : DbContext
 {
@@ -187,7 +186,7 @@ b) classes to keep the database up-to-date with CRUD operations
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DbContext as a Service

  • In Program.cs, add the context to services with AddDbContext method
    • @@ -204,7 +203,7 @@ services.AddControllers().AddNewtonsoftJson();
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Migrations

  • As the development progresses, models and database schemas change over time @@ -220,7 +219,7 @@ services.AddControllers().AddNewtonsoftJson();
  • EFCore migrations have built-in version control; a snapshot of each version of the schema is stored
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Applying migrations

  • Open the Package Manager Console in Visual Studio @@ -241,7 +240,7 @@ services.AddControllers().AddNewtonsoftJson();
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  • At this point, the values you have entered (Contacts table in this example) should show up in the database. You can check it up e.g. in pgAdmin.
@@ -262,7 +261,7 @@ services.AddControllers().AddNewtonsoftJson();
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Exercise 1: Adding Context

Continue working on the CourseAPI.

@@ -275,7 +274,7 @@ services.AddControllers().AddNewtonsoftJson();
  • Check that the Course table with the starting values has appeared to the database
    • -
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    Using DbContext in the API

    • Because DbContext is added to services, it can be accessed from any other service, such as the repository
      • @@ -289,7 +288,7 @@ services.AddControllers().AddNewtonsoftJson();
    • After modifying the DbSet, update the changes to the database with the DbContext.SaveChanges() method
    -
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    Injecting DbContext

    • Inject the DbContext to your repositories as you would any other service:
      public class ContactRepository : IContactRepository
@@ -306,7 +305,7 @@ services.AddControllers().AddNewtonsoftJson();
    -
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    DbContext: Read Operations

    public class ContactRepository : IContactRepository
 {
@@ -321,7 +320,7 @@ services.AddControllers().AddNewtonsoftJson();
 }
    -
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    DbContext: Create Operations

    public class ContactRepository : IContactRepository
 {
@@ -339,7 +338,7 @@ services.AddControllers().AddNewtonsoftJson();
 }
    -
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    DbContext: Update Operations

    public class ContactRepository : IContactRepository
 {
@@ -360,7 +359,7 @@ services.AddControllers().AddNewtonsoftJson();
 }
    -
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    DbContext: Delete Operations

    public class ContactRepository : IContactRepository
 {
@@ -378,7 +377,7 @@ services.AddControllers().AddNewtonsoftJson();
 }
    -
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    Exercise 2: CRUD on the DB

    Continue working on CourseAPI.

    @@ -387,7 +386,7 @@ services.AddControllers().AddNewtonsoftJson();
  • Test with Postman. Keep refreshing the DB in pgAdmin or creating queries with psql to make sure the requests work as intended
    • -
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    Summing Things Up

    • Now the API has been hooked up to a PostgreSQL database
      • @@ -396,7 +395,7 @@ services.AddControllers().AddNewtonsoftJson();
    • Controllers accepting HTTP requests have access to the repository
    -
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    EFCore Code First Checklist

    1. Install required packages
      2. @@ -406,7 +405,7 @@ services.AddControllers().AddNewtonsoftJson();
    2. Add CRUD operations to the database repository
    -
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    Modifying the Relations

    • Let's change the structure of our Contacts API by adding a new class Account @@ -418,7 +417,7 @@ services.AddControllers().AddNewtonsoftJson();
    • Emails will be removed from the Contacts table
    -
    +
    // Models/Contact.cs
 public class Contact
 {
@@ -438,13 +437,13 @@ services.AddControllers().AddNewtonsoftJson();
 }
    -
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    • Adding a migration at this point will result in a warning:
    -
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      @@ -466,7 +465,7 @@ services.AddControllers().AddNewtonsoftJson();
    -
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    Exercise 3: Adding Migrations

    Continue working on CourseAPI.

    @@ -477,10 +476,10 @@ services.AddControllers().AddNewtonsoftJson();
  • Update the database. Check that the changes show up in the database with pgAdmin
    • -
    +

    Database First approach

    -
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    What is the Database First approach?

    • This is the other approach for creating a connection between the database and the application
      • @@ -495,7 +494,7 @@ services.AddControllers().AddNewtonsoftJson();
    -
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    Scaffolding

    • Use the Package Manager Console to "reverse engineer" the code for an existing database @@ -509,7 +508,7 @@ services.AddControllers().AddNewtonsoftJson();
    • Using the connection string corresponding to your database, this will create all the classes for the entities in the DB as well as the context class
    -
    +

    Exercise 4: Database First

    Create a new ASP.NET Core web app using the API template.

    @@ -520,13 +519,13 @@ b) by copying the <PackageReference> lines from the .cs
  • Scaffold the sqlpractice database created in SQL Databases Exercise 1 to the project by using the Database First approach. If you have not yet created the database in PostgreSQL, it can be found here
    • -
    +

    Reading: Authentication with roles

    • Here's an example how to do a role-based authentication by using JWT tokens
    -
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    Exercise 5 (Extra): Connection

    Continuing the previous exercise,

    diff --git a/6-databases-with-entity-framework.md b/6-databases-with-entity-framework.md index 67ccb11..c121ee7 100644 --- a/6-databases-with-entity-framework.md +++ b/6-databases-with-entity-framework.md @@ -16,10 +16,8 @@ title: 5. Databases with Entity Framework - [Entity Framework (EF)](#entity-framework-ef) - [Code First approach](#code-first-approach) - [Migrations](#migrations) -- [Migrations](#migrations) - [Database First approach](#database-first-approach) - ## Entity Framework (EF) * This lecture will assume you have a basic understanding of SQL databases diff --git a/README.md b/README.md index 16ff1d3..5c6d182 100644 --- a/README.md +++ b/README.md @@ -9,4 +9,4 @@ | 5 | [Model Validation & API Design](5-model-validation-and-designing-apis.md) | [Download slides](5-model-validation-and-designing-apis-slides.html?raw=1) | | 6 | [Databases with Entity Framework](6-databases-with-entity-framework.md) | [Download slides](6-databases-with-entity-framework-slides.html?raw=1) | | 7 | [Authentication and Authorization](7-authentication-and-authorization.md) | [Download slides](7-authentication-and-authorization-slides.html?raw=1) | -| 8 | [Testing](8-testing.md) | [Download slides](8-testing-slides.html?raw=1) | +| 8 | [Testing](8-testing.md) | [Download slides](8-testing-slides.html?raw=1) | \ No newline at end of file