T02D02

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Contents

1. Chapter I
   1.1. Level 2. Room 1.
2. Chapter II
   2.1. PostgreSQL.
   2.2. API and ASP.NET Core.
3. Chapter III
   3.1. Quest 1. Connect.
   3.2. Quest 2. Model update.
   3.3. Quest 3. Migration.
   3.4. Quest 4. CRUD Awakens.
   3.5. Quest 5. Testing Grounds.

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Chapter I

Level 2. Room 1.

LOADING LEVEL 2...

SUCCESSFULLY LOADED.

> Look around

You wake up in a new room.
It feels familiar — the same walls, the same desk, but now there’s a new system unit on it, with the words PostgreSQL SERVER engraved in large letters.
The monitor displays the message:

CONNECTION LOST.
PLEASE ESTABLISH LINK TO DATABASE.

Next to the monitor lies a piece of paper with notes from the previous operator:

“The AI knows too much. Without a database, it loses its memory after every reboot.
Create a stable storage for it. Connect the server.
Be careful: the database is alive.
It remembers everything.”

> Turn on the computer

The screen displays a prompt:

> psql -U postgres

LOADING... CONNECTION MODULE READY

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Chapter II

PostgreSQL

PostgreSQL is a powerful open-source object-relational database management system.
It supports transactions, relationships between tables, triggers, functions, and much more.
Unlike simple databases, PostgreSQL integrates deeply with applications and allows storing complex data structures.

Basic PostgreSQL commands:

# connect
psql -U postgres

# create database
CREATE DATABASE mydatabase;

# show tables
\dt

# execute SQL queries
SELECT * FROM "Orders";

PostgreSQL is often used in ASP.NET Core projects for its stability, open license, and great Entity Framework Core support.

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API and ASP.NET Core

ASP.NET Core is a modern cross-platform framework for building web applications and APIs.
It enables you to write fast RESTful services that can interact with databases via Entity Framework Core.

Typical Web API project structure:

/Controllers
    OrderController.cs
    ProductController.cs
/Models
    Order.cs
    Product.cs
/Context
    AppDbContext.cs
Program.cs
appsettings.json

Main concepts:

• Controller — handles HTTP requests and responses.
• Model — describes data (tables in the database).
• DbContext — provides a link between code and the database.
• Migration — creates or modifies the database schema based on models.
• Dependency Injection — injects dependencies (e.g. AppDbContext into controllers).

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Chapter III

Quest 1. Connect.

> Look at the screen

The monitor still shows the same message:

CONNECTION LOST.
PLEASE ESTABLISH LINK TO DATABASE.

== Quest 1 received. Connect PostgreSQL to your ASP.NET Core project. ==

Tasks:

1. Install PostgreSQL and create a new database (for example, game_ai_db).
2. Add the connection string in AppDbContext.
3. Configure the DbContext to use Npgsql (PostgreSQL provider).
4. Verify the connection using dotnet ef database update or a manual SQL query.

HINT:
Don’t forget to register AppDbContext in Program.cs via builder.Services.AddDbContext<AppDbContext>().

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Quest 2. Model update.

The AI speaks again through the terminal:

“Memory structured, but data insufficient.
Add a new dimension of time.”

== Quest 2 received. Add a new field to the Order model — order date. ==

Tasks:

1. In Order.cs, add a new property.
2. Update the migration so the field appears in the database.
3. Commit the changes to version control.

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Quest 3. Migration.

AI:

“Storage created. But it is empty. Awaken the structure of data.”

== Quest 3 received. Perform database migration. ==

Tasks:

1. Add a migration:

   dotnet ef migrations add MigrationName

2. Apply the migration:

   dotnet ef database update

3. Make sure the tables appeared in PostgreSQL (via psql or pgAdmin).

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Quest 4. CRUD Awakens.

AI (with a faint echo):

“You taught me to remember.
Now teach me to act.”

== Quest 4 received. Implement Post and Put methods in OrderController. ==

Tasks:

1. Add methods to OrderController:
   • POST /api/order — create a new order
   • PUT /api/order/{id} — update an existing order
2. Test endpoints via Postman or Swagger.
3. Commit the changes to git.

(optional):
Create a CRUD controller for Products.

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Quest 5. Testing Grounds.

> The screen displays:

“Verification complete.
Connection stable.
Data alive.
But can they withstand the load?..”

== Quest 5 received. Test the API. ==

Tasks:

1. Use Swagger or Postman to test CRUD operations.
2. Ensure records can be created, updated, and deleted.
3. Commit your changes with message:

   feat: added database integration and CRUD operations
   

LOADING...
DATA LINK ESTABLISHED
DOOR TO NEXT LEVEL — UNLOCKED