Topic 10. Creating and consuming REST web services: ASP.NET Core Minimal API, HttpClient, and JSON

Goal: get to know the HTTP protocol, the REST architectural style, and the JSON format; learn to build ASP.NET Core Minimal API web services with routes, parameter binding, validation, and ProblemDetails responses, and to document and test them with OpenAPI and .http files; master consuming web services from C# programs through HttpClient and IHttpClientFactory.

Lecture contents

1. HTTP, REST, JSON, and Minimal API — The HTTP protocol · The REST architectural style · The JSON format and System.Text.Json · An ASP.NET Core Minimal API project
2. Routes, results, and validation — Endpoints and routes · Results, validation, and errors
3. Documentation and the database — Documentation and testing · Connecting a database through EF Core
4. The HttpClient client and security — The HttpClient client · CORS and authentication (overview)
5. Common mistakes — Common mistakes

Practice and review

• Practice — 3 worked examples with complete code and execution results
• Tasks — 30 variants, each with tasks at three difficulty levels
• Summary — conclusions, self-check questions, and useful links