CampusHub

A course enrollment platform built as a .NET microservices sandbox: teachers publish courses with a limited number of seats, students enroll, and each enrollment runs as a saga across services.

Architecture

Part	Role
BE/Gtw	YARP gateway and BFF: OpenID Connect sign-in, HttpOnly cookie session, tokens attached server side, CSRF check, serves the Blazor front
BE/Catalog	Courses and seat reservations (MongoDB, optimistic concurrency)
BE/Enrollment	Enrollment saga on Dapr Workflow (hold a seat, confirm it, compensate on failure), transactional outbox on MongoDB, Hangfire jobs
BE/Notification	Idempotent subscriber of the enrollment events, "my notifications"
BE/Grading, BE/Billing	Scaffolded services
FE/CampusHub.Web	Blazor WebAssembly front, MVVM (CommunityToolkit.Mvvm), thin views over plain C# ViewModels
Aspire	Local orchestration: MongoDB replica set, RabbitMQ, Redis, Dapr sidecars, OpenTelemetry dashboard
Dapr	Components per environment: RabbitMQ pub/sub, Redis state store, resiliency policies, subscriptions

Each service follows the same layers: Domain (aggregates returning FluentResults results, no exceptions for expected refusals), UseCases, FrontendApi / ServiceApi (minimal APIs, ProblemDetails), Infrastructure and Host.

Enrollment flow: the front sends a request with an idempotency key → Enrollment stores it and starts the workflow → the workflow reserves a seat in Catalog, then confirms it (or releases it) → the confirmation is written with an outbox message in the same MongoDB transaction → the dispatcher publishes it through Dapr to RabbitMQ → Notification stores a notification, ignoring duplicates.

Stack

.NET 11 · ASP.NET Core minimal APIs · YARP · Dapr (Workflow, pub/sub, state, resiliency) · RabbitMQ · MongoDB · Redis · Hangfire · .NET Aspire · OpenTelemetry + Serilog · Blazor WebAssembly (MVVM) · FluentResults · xUnit, Testcontainers · Arc4u framework

Run it

Requirements: .NET 11 SDK (see global.json), Docker, Dapr CLI with dapr init (runtime 1.18 or later).

Front only, with an in-memory backend:

dotnet run --project FE/CampusHub.Web -p:WasmApplicationEnvironmentName=Demo

Then open http://localhost:5280.

Everything (containers, services, sidecars, gateway):

dotnet run --project Aspire

The gateway listens on https://localhost:7184. The services need an OpenID Connect client and the Arc4u decryption certificate; their secrets are read from Configs/appsettings.Development.local.json next to each service's appsettings.Development.json, a file that is not committed.

Roles: every signed-in user is a student. Teachers (create and publish courses) and administrators (Swagger, Hangfire dashboards) come from the identity provider (campushub:teach / campushub:admin permissions) or, locally, from the AppHost user secrets:

dotnet user-secrets set CampusHub:Teachers "<user id>" --project Aspire

The user id is shown on the Teaching page to a signed-in user who is not a teacher yet.

Tests:

dotnet test CampusHub.slnx

The outbox tests start a MongoDB replica set with Testcontainers, so Docker must be running.