Dive into ASP.NET Core Copilot: Your First Concrete Step Today
ASP.NET Core Copilot: The Essentials in One Article — Real Code, Diagrams, and Concrete Steps, Excerpts from a 43-Lesson Course.
The best way to learn ASP.NET Core Copilot is by doing. This article gives you a head start with practical excerpts from a 43-lesson course — enough to get your first results today.
- Introduction and Installation
- ASP.NET Core Fundamentals
- Create a REST API with Copilot
- Entity Framework Core Fundamentals
- LINQ and Advanced Queries
Unit tests with xUnit and Moq
Learning objectives
- Create an xUnit test project in the solution
- Write a test with
[Fact]and the Arrange-Act-Assert pattern - Parameterize a test with
[Theory]and[InlineData] - Create a mock of a dependency with Moq
- Verify that a mocked method was called
The intuition: testing a part without assembling the whole machine
A unit test verifies a single unit of code (usually a method) in isolation. We do not want to touch the real database or a remote service: it is slow and unpredictable. We therefore replace these dependencies with mocks, controlled stand-ins. It is like testing an engine on a test bench rather than driving the entire car after every change.
Create the test project
Parameterized tests with [Theory]
To test multiple data sets without duplicating code, use [Theory]:
Configuration with appsettings.json
appsettings.json, manage multiple environments, and use the Options pattern.Learning objectives
- Read values from
appsettings.json - Understand the hierarchy of configuration sources
- Manage multiple environments (Development, Production)
- Bind a configuration section to a class (Options Pattern)
- Protect sensitive secrets
The intuition: externalizing what changes
Code should never contain hard-coded values such as a connection string or an API key. These values change depending on the environment (your machine, the test server, production). They are therefore placed in external configuration files.
ASP.NET Core reads configuration from multiple sources, in a precise priority order. A higher-priority source overrides values from a lower-priority source.
| Source | Priority | Typical usage |
|---|---|---|
appsettings.json | Low | Default values |
appsettings.{Env}.json | Medium | Per environment |
| Environment variables | High | Production, secrets |
| Command-line arguments | Very high | One-off overrides |
Read a simple value
Here is an appsettings.json file and how to read its values:
Joins and eager loading (Include, ThenInclude)
Include and ThenInclude, and understand how to avoid the dreaded N+1 problem.Learning objectives
- Load a relationship with
Include - Load a nested relationship with
ThenInclude - Recognize the N+1 problem
- Distinguish eager, lazy and explicit loading
- Measure the impact on the number of SQL queries
The intuition: bringing the neighborhood back in one go
When you load a product, its related category is not loaded automatically. If you access it without doing anything, you get null (or an extra query). Include tells EF: “when you load the products, also bring back their category, in a single query”.
Without Include (N+1)
With Include
Eager, lazy and explicit loading
| Strategy | When to load | How |
|---|---|---|
| Eager | Immediately | Include |
| Explicit | On demand | Entry().Load() |
| Lazy | On access | Proxies (can cause N+1) |
Include): it is explicit and predictable. Lazy loading is convenient but hides queries and can reintroduce N+1 without you noticing.This article covers the most useful excerpts — the full ASP.NET Core Copilot course (11 chapters, 43 lessons, corrected exercises and final project) takes you all the way.
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