ASP.NET Core Web API

ASP.NET Core Web API is a framework for building RESTful web services. It allows us to expose data and business logic to the web using HTTP. In this article, we will learn how to:

• Create a web API project

• Add model classes and a database context

• Scaffold a controller with CRUD methods

• Configure routing and URL paths

• Call the web API from a client

• Add authentication and authorization

• Deploy the API

Creating the Project

We can create a Web API project in ASP.NET Core using any of these options:

• Visual Studio

• Visual Studio Code

• Visual Studio for Mac

• .NET CLI

For example, using the .NET CLI we can run:

dotnet new webapi -o TodoApi
cd TodoApi

This will create a new Web API project named TodoApi.

Adding Model Classes

We define model classes to represent the data our API will manage. For example, a TodoItem class:

public class TodoItem 
{
    public long Id { get; set; } 
    public string Name { get; set; }  
    public bool IsComplete { get; set; }
}

Adding a Database Context

We create a database context class that derives from DbContext:

public class TodoContext : DbContext
{
    public TodoContext(DbContextOptions<TodoContext> options)   
        : base(options) { }

    public DbSet<TodoItem> TodoItems { get; set; }
}

We then register the context with Dependency Injection in Program.cs:

builder.Services.AddDbContext<TodoContext>(opt =>
    opt.UseInMemoryDatabase("TodoList"));

Scaffolding a Controller

We can scaffold a controller with CRUD methods using:

dotnet aspnet-codegenerator controller ...

This will generate a controller class marked with the [ApiController] attribute and methods to GET, POST, PUT and DELETE todo items.

Configuring Routing

We use attribute routing to define the URL paths for our API. For example:

[Route("api/[controller]")]
[ApiController]
public class TodoItemsController : ControllerBase
{
    [HttpGet]
    public IActionResult Get() { ... }

    [HttpGet("{id}")]
    public IActionResult Get(int id) { ... }
}

This will map to the URLs:

• /api/todoitems

• /api/todoitems/{id}

Calling the API

We can call the API from:

• JavaScript

• Postman

• cURL

• Mobile clients

For example, using cURL:

curl -X GET "https://localhost:5001/api/todoitems"

Authentication and Authorization

We can secure our API using:

• JWT Bearer Tokens

• Azure Active Directory

• OAuth2 / OpenID Connect (using IdentityServer4)

Deploying the API

We can deploy our API to:

• Azure App Service

• AWS Elastic Beanstalk

• Heroku

• Docker

Hope this helps! Let me know if you have any other questions.

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