Data Layer

Goal

This snapshot advances Northline Press by teaching you to persist authors and posts with EF Core and PostgreSQL.

Every numbered folder is a complete app. Run this stage independently, then compare it with the previous folder.

Prerequisites

Use .NET 8 SDK, a terminal, and Docker for Postgres stages. You should recognize C#, HTTP verbs, and basic HTML.

Port 5080 must be free. Copy .env.example and review appsettings.json before database stages.

• .NET 8 SDK
• A code editor and terminal
• Docker from part 4 onward

Concepts

EF Core maps C# entities to tables. Each snapshot uses its own northline database so stages stay independent.

Keep page models thin: Razor Pages accept input, services and EF Core enforce rules, and Razor escapes output by default.

Walkthrough

Register AppDbContext with Npgsql, create User and Post entities, seed Ada and Grace, and list posts on the home page.

Read the example, then open the matching snapshot. The repository includes the surrounding setup and error handling.

builder.Services.AddDbContext<AppDbContext>(o => o.UseNpgsql(connectionString));

Run and verify

Enter 04-Data-Layer, restore packages, and run on port 5080.

Open http://127.0.0.1:5080. Watch the terminal for validation and database errors.

docker compose up -d
git clone https://github.com/michaeldunga1/fcc-aspnet-blog.git
cd fcc-aspnet-blog/04-Data-Layer
cp .env.example .env
dotnet restore
dotnet run --urls http://127.0.0.1:5080

Troubleshooting

Connection refused usually means Docker Postgres is stopped or the port is not 5436.

Restore errors usually mean the SDK is missing or you opened the wrong folder. For Postgres failures, confirm Docker is running and the northline_NN database name matches the snapshot.

• Read the first error first
• Restart after environment changes
• Never commit .env or production secrets

Try this

Add a minimum title length check before insert.

Test a happy path and one invalid or unauthorized request.

• Make one small change
• Test it in the browser
• Compare with the next snapshot only after it works