Build Web APIs with ASP.NET Core (.NET 10) in the Age of AI

A deep dive into a “working” API to uncover hidden design flaws—validation gaps, lack of structure, and misleading success responses—and understand why such implementations fail in real-world systems.

A quick, hands-on preview of how small validation changes can completely transform API behavior—shifting from blindly accepting input to enforcing correctness and building a more reliable system.

A clear mental model to evolve your API from “just working” to truly production-ready—by moving from basic functionality to correctness, and finally to systems that handle real-world failures, scale, and unpredictability.

This lecture breaks down the full execution flow of an API call in ASP.NET Core, showing how a request moves through the pipeline, reaches your controller, and returns a response—so you can think in systems, not just endpoints.

This lecture breaks the illusion of “controller-driven APIs” and introduces the real execution model of ASP.NET Core—a middleware pipeline. You’ll understand how every request flows through ordered components, how each step can control behavior, and why pipeline design—not controllers—defines how your system actually works.

In this lecture, we turn the pipeline from a concept into real execution by using middleware to observe what happens before and after your controller. You’ll see how requests are actually processed, why await next() controls the flow, and how this pattern becomes the foundation for logging, authentication, and other production-level behavior.

In this lecture, you’ll break down Program.cs line by line to understand how your API is wired — from services and middleware to routing and execution — so you know exactly how your system comes alive and what breaks when it’s misconfigured.

In this lecture, we move beyond isolated APIs and integrate a real frontend, uncovering how browser security blocks cross-origin calls and how CORS enables controlled communication. You’ll see the system break, understand why it happens, and fix it the right way—by configuring access at the API boundary, not hacking around it.

In this lecture, we break down how data actually enters your API through model binding. You’ll learn how route, query, and body inputs are mapped to your code, why implicit binding can lead to bugs, and how to make input handling explicit, predictable, and easier to debug in real-world systems.

Learn how to design validation as a system—not just write checks—by exploring different approaches, understanding their trade-offs, and choosing a scalable strategy to protect your API from invalid input.

In this lecture, we evolve from custom validation enforcement to the framework’s built-in approach using [ApiController]. You’ll see how it automatically enforces ModelState, how it compares to our global filter, and how to think about the trade-off between simplicity and control in real-world APIs.

Learn how to use HTTP status codes and IActionResult to make your API communicate intent clearly, enabling predictable client behavior and production-ready integrations.

Learn how to standardize error responses in your ASP.NET API using ProblemDetails. In this lesson, we’ll see how consistent error structures make client integrations easier, reduce bugs, and keep your API predictable at scale—without writing custom error-handling code.

In this lecture, we expose how controllers naturally grow into “fat controllers” as new requirements are added. What starts as simple and clean quickly becomes a mix of validation, business logic, and data handling. You’ll see why this approach works initially but creates long-term problems, setting the stage for introducing proper structure with services and dependency injection.

In this lecture, we introduce the service layer by moving all business logic out of controllers into a dedicated OrderService. You’ll see how this simple structural change improves clarity, enforces separation of concerns, and sets the foundation for scalable, maintainable APIs.

This lecture builds a clear mental model for Dependency Injection by focusing on why it exists, not just how to use it. We explore how direct object creation leads to tight coupling, introduce IOrderService for abstraction, and intentionally stop short of solving the problem—setting up the need for a DI container in the next lecture.

Before implementing Dependency Injection in our Orders API, this lecture builds a clear mental model of how ASP.NET Core handles service creation and lifetimes, so you understand how your system actually behaves at runtime—not just how the code looks.

In this lecture, we move from concept to implementation by wiring Dependency Injection into our Order API. We replace manual object creation with framework-managed dependencies, register services in the container, and shift control of lifecycle and instantiation to the system—turning working code into a properly structured, scalable foundation.

We examine why our current API, while functional, fails to model real-world behavior — exposing the need for proper domain modeling with relationships, rules, and system-owned logic.

Transform a flat API into a real system by introducing domain models, adding business logic, enforcing relationships, and validating data—shifting control from client input to system-driven behavior.

This lecture is a reality check where we step back and examine how our Order API has evolved from a simple demo into a system with real complexity. We identify where things are starting to break—mixed responsibilities, growing dependencies, and fragile code—and set the stage for why proper design and separation of concerns are now essential.

This lecture exposes a subtle but critical flaw in our current API design—directly exposing domain models. You’ll see how this creates tight coupling, why even small changes break clients, and why a “working” API isn’t necessarily a usable one. By the end, you’ll clearly understand why APIs must be treated as stable contracts, not reflections of internal structure.

Learn how to introduce a contract boundary using DTOs and mapping so your API no longer exposes internal models, enabling safe evolution without breaking clients.

Learn how to design APIs that feel predictable and easy to use by enforcing consistent response structures and resource-based patterns—so your system scales without confusing clients or breaking integrations.

In this lecture, we bring everything together—refactoring our API to enforce clear boundaries, centralize mapping with AutoMapper, and deliver a clean, consistent, consumer-friendly contract that’s ready for real-world use.

This lecture exposes why storing data in memory is fundamentally flawed for real systems. You’ll see how it leads to data loss, inconsistency across instances, and unreliable behavior—setting the stage for introducing real persistence using Entity Framework Core and SQL Server.

Set up EF Core, connect your API to SQL Server, and establish the foundation for real data persistence beyond in-memory storage.

In this lecture, we move beyond setup and actually prove persistence works by writing data to the database, storing it reliably, and retrieving it through real API flows—validating the complete lifecycle of a production-ready system.

In this lecture, we introduce EF Core migrations to safely evolve the database schema, moving from a fragile setup to a version-controlled system where changes are tracked, applied incrementally, and executed without breaking existing data.

In this lecture, we move beyond “working APIs” and expose how naive designs fail under real-world scale. By building a simple Product API and pushing it with large data, you’ll see how returning everything leads to slow responses, heavy payloads, and system-wide degradation. This sets the foundation for designing APIs that control data flow and behave predictably in production.

In this lecture, we evolve our API from simply limiting data to intelligently shaping it. You’ll implement pagination to control response size, then add filtering and sorting to return only relevant, well-ordered data. By the end, the API behaves like a real query interface—predictable, efficient, and ready for production-scale usage.

Learn how to evolve APIs safely by distinguishing between additive and breaking changes, and applying versioning only when necessary—so you can introduce new features without breaking existing clients.

Learn how to make your API truly usable by exposing clear, consumer-friendly documentation using Swagger—so developers can understand, explore, and integrate without guesswork.

This lecture sets the foundation for API security by introducing how real systems think about identity and control. You’ll understand why open APIs are inherently vulnerable, the difference between authentication and authorization, and how JWT enables identity to flow across requests. More importantly, it builds the mental model we’ll use to evolve our Order API from a fully open system to a secure, production-ready architecture.

This lecture focuses on integrating JWT authentication into the API pipeline so the system can recognize and validate identity on incoming requests. You’ll configure the necessary services and middleware, and understand how authentication runs automatically before your controllers. By the end, the API remains open externally—but internally, it becomes identity-aware, setting the foundation for enforcing security in the next steps.

This lecture implements the first complete authentication flow by adding a login endpoint, generating a JWT token, and using it in API requests. You’ll see how identity is created, carried by the client, and validated by middleware—turning the system from capable to actually functional.

This lecture turns authentication into real control by introducing role-based authorization. You’ll secure endpoints using roles, update the login flow to issue role-based tokens, and see how the same API behaves differently for users vs admins—moving from simple protection to true, enforceable access control.

This lecture transforms authentication from a working demo into a production-ready system. You’ll implement secure user storage with hashing, introduce proper registration, and refactor login to use real data—ensuring that identity, security, and system behavior are all driven by a consistent and reliable foundation.