build-web-api-dotnet-8

ASP.NET Core Todo API — Minimal Fundamentals Sample

A focused .NET 10 companion showing how core ASP.NET Core Web API building blocks work together in a small Todo API.

Full tutorial

ASP.NET Core Fundamentals: Build Web APIs on .NET 8

Framework note

The tutorial explains ASP.NET Core 8.

This companion targets .NET 10 so it can use the DOTNET GUIDE repository's current SDK and CI toolchain. The sample demonstrates the same foundational routing, dependency-injection, request-binding, middleware, CRUD, and HTTP-result patterns.

What this sample demonstrates

• Minimal API route groups;
• route parameters and constraints;
• JSON request-body binding;
• dependency injection into route handlers;
• an in-memory repository;
• GET, POST, PUT, and DELETE operations;
• validation responses;
• 200, 201, 204, 400, and 404 semantics;
• a Location header after resource creation;
• a small request-ID middleware;
• integration testing with WebApplicationFactory<Program>.

Important boundary

This repository sample intentionally does not reproduce the complete tutorial.

The full DOTNET GUIDE tutorial also covers:

• controllers and MVC patterns;
• configuration sources;
• EF Core and SQLite;
• migrations;
• JWT authentication and authorization;
• caching;
• rate limiting;
• health-check strategy;
• performance guidance;
• migration from ASP.NET Core 7;
• deployment options.

The separate repository sample aspnet-core/api-security-in-practice contains a focused security example.

Prerequisite

• .NET 10 SDK

Check:

dotnet --version

Restore, build, and test

dotnet restore .\TodoApiMinimal.slnx

dotnet build `
  .\TodoApiMinimal.slnx `
  --configuration Release `
  --no-restore

dotnet test `
  .\TodoApiMinimal.slnx `
  --configuration Release `
  --no-build

Run

dotnet run `
  --project .\src\TodoApiMinimal\TodoApiMinimal.csproj `
  --urls http://localhost:5128

Endpoints

GET    /
GET    /health
GET    /api/todos
GET    /api/todos/{id}
POST   /api/todos
PUT    /api/todos/{id}
DELETE /api/todos/{id}

Example request

$body = @{
  title = "Review HTTP status codes"
} | ConvertTo-Json

Invoke-RestMethod `
  -Method Post `
  -Uri "http://localhost:5128/api/todos" `
  -ContentType "application/json" `
  -Body $body

Persistence limitation

The repository is stored only in application memory.

Restarting the process resets the sample to its two seeded Todo items.

No production persistence is implied.

Project structure

TodoApiMinimal.slnx
README.md
src/
└── TodoApiMinimal/
    ├── TodoApiMinimal.csproj
    └── Program.cs
tests/
└── TodoApiMinimal.Tests/
    ├── TodoApiMinimal.Tests.csproj
    └── TodoApiTests.cs

Deliberately omitted

• controllers;
• EF Core;
• SQLite;
• migrations;
• authentication;
• authorization;
• CORS;
• caching;
• rate limiting;
• Swagger or OpenAPI UI;
• Docker;
• cloud deployment;
• production storage.

These are covered by the full tutorial or another focused companion sample.

Verification

• Companion target framework: .NET 10
• Tutorial framework: .NET 8
• External services required: none
• API keys required: none
• Database required: none
• Expected integration tests: 7
• Last reviewed: 2026-07-31

This sample is educational and should be reviewed before production use.