ASP.NET Core API For Beginners

Building and Working with Web APIs in ASP.NET Core

1. Introduction to APIs

• What is an API?
  • Explanation of APIs (Application Programming Interfaces).
  • Difference between Web API and Web Services.
  • Understanding RESTful APIs:
    • Stateless, resource-based APIs.
    • HTTP verbs (GET, POST, PUT, DELETE) and their roles in APIs.
• Why Build APIs with ASP.NET Core?
  • Lightweight, high-performance framework for building APIs.
  • Cross-platform capabilities (Windows, macOS, Linux).
  • Integration with modern front-end frameworks (React, Angular, etc.).

2. Setting up an ASP.NET Core Web API Project

• Creating a Web API Project

  • Using Visual Studio or Visual Studio Code to create a new API project.
  • Choosing the correct project template (ASP.NET Core Web API template).

• Project Structure for APIs

  • Overview of important files and folders:
    • Controllers: Contains API controllers.
    • Startup.cs or Program.cs: Configuring services and middleware.
    • appsettings.json: Configuration settings, including connection strings.

3. Building Your First API

• Creating a Controller
  • What is an API controller? How is it different from an MVC controller?
  • Creating a new controller that inherits from ControllerBase.
• Action Methods and HTTP Verbs
  • Defining action methods to handle HTTP requests (GET, POST, PUT, DELETE).
  • Return types: IActionResult, ActionResult, and HTTP status codes (200 OK, 404 Not Found, 400 Bad Request, etc.).

4. Routing in Web API

• Understanding Attribute Routing
  • How to define routes using attributes ([Route("api/[controller]")], [HttpGet], [HttpPost], etc.).
  • Defining route parameters ([HttpGet("{id}")]).
  • Using convention-based vs attribute-based routing.

5. Handling Data with DTOs (Data Transfer Objects)

• What are DTOs?

  • Purpose of DTOs in APIs (separation of concerns, security, optimization).
  • Creating simple DTO classes to shape data for API responses and requests.

• Mapping Between Entities and DTOs

  • Using manual mapping or libraries like AutoMapper to map between your domain models and DTOs.

6. Implementing CRUD Operations

• Connecting to a Database with EF Core

  • Setting up Entity Framework Core in your API project.
  • Configuring a database connection (using SQL Server or SQLite).
  • Creating and managing database tables for your API (using migrations).

• CRUD Operations

  • GET: Retrieving data (e.g., fetching all records or a specific item by ID).
  • POST: Creating a new resource.
  • PUT/PATCH: Updating an existing resource.
  • DELETE: Deleting a resource.

7. Error Handling and Validation

• Input Validation

  • Using Data Annotations for input validation (e.g., [Required], [MaxLength], etc.).
  • Validating incoming data to ensure it meets specific rules.

• Error Handling

  • Global error handling in ASP.NET Core.
  • Returning appropriate status codes for different scenarios (400 for bad requests, 500 for server errors, etc.).
  • Using ModelState.IsValid to check if the incoming data is valid.

8. Authentication and Authorization

• Securing Your API
  • Overview of API security principles.
  • Introduction to JWT (JSON Web Tokens) for authentication.
• Protecting Endpoints with Authentication
  • Configuring JWT Bearer Authentication in ASP.NET Core.
  • Securing specific routes using the [Authorize] attribute.
• Role-Based Authorization
  • Restricting access to endpoints based on user roles.

9. Versioning Your API

• Why API Versioning Matters
  • Handling changes in your API over time while maintaining backward compatibility.
• Implementing API Versioning
  • Using ASP.NET Core's built-in API versioning tools.
  • Defining versions in URLs, headers, or query strings (e.g., api/v1/products).

10. Testing and Documentation

• Testing Your API

  • Using Postman or Swagger to test your API endpoints manually.
  • Writing unit tests for your API controllers using testing frameworks (e.g., xUnit, Moq).

• Generating API Documentation with Swagger

  • Integrating Swagger (OpenAPI) into your project for automatic API documentation.
  • Configuring Swagger to generate interactive documentation of your endpoints.

11. Deployment

• Publishing Your API
  • How to publish your API to a hosting platform (Azure, AWS, Docker, etc.).
  • Deploying your API to Azure App Service.
  • Containerizing your API using Docker for easier deployment across environments.

Project: Building a Product Catalog API

In this project, learners will create a simple Product Catalog API where users can:

• List all products (GET).
• View a single product by ID (GET).
• Create a new product (POST).
• Update an existing product (PUT).
• Delete a product (DELETE).

The API will connect to a SQL Server database using Entity Framework Core, and learners will secure the API using JWT authentication.