Tutorials ASP.NET Core Web API Tutorial
Introduction to ASP.NET Core Web API — Complete Guide
Introduction to ASP.NET Core Web API — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of ASP.NET Core Web API Tutorial on Toolliyo Academy.
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ASP.NET Core Web API Tutorial · Lesson 10 of 100
API Request Lifecycle in ASP.NET Core
Beginner → Intermediate → Advanced → Professional
Beginner · 1 — API foundations · ~6 min · Module 1: Web API Fundamentals
What is this?
When a client calls your API, Kestrel receives bytes, middleware runs in order (HTTPS, auth, logging), routing picks an action, model binding fills parameters, the action runs, result filters format the response, and JSON goes back.
Why should you care?
Understanding the pipeline helps you know where to put auth, exception handling, and logging — not inside every controller method.
See it live — copy this example
Create a Web API (dotnet new webapi), paste the example, run dotnet run, test in Swagger.
Client → Kestrel → Middleware pipeline → Routing
→ Model binding → Controller action → Service → EF Core
→ Map to DTO → JSON + status code → ClientRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- Order matters: UseAuthentication before UseAuthorization.
- Exception middleware early catches errors from later stages.
- MapControllers is where endpoints attach.
Try it yourself
- Add a simple middleware that logs method and path.
- Place it before MapControllers and watch console on each request.
- Draw the pipeline on paper for one POST /api/products call.
- Change a route URL or DTO property and save — test again in Swagger or curl.
- Return the wrong status code on purpose (404 instead of 200) and see what the client shows.
Remember
Request flows through middleware then routing then action. Configure cross-cutting concerns in middleware, not controllers. Program.cs order is part of the interview checklist.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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