Mastering Modern .NET Architecture

Architectural Principles

Good architecture is about making good decisions over time, not about following rules or trends. This module explains why clear principles help teams make consistent choices and avoid confusion as systems and requirements change.

• The role of an Architect
• What is good Architecture?
• Architectural Principles: Encapsulation, Separation of Concerns, ...
• Architectural Drivers

N-Tier Architecture

N-Tier architecture is still very common, often because it feels familiar and safe. This module explains why it became popular, what it does well, and why it can become a problem when applications grow larger.

• What is N-Tier?
• Physical Tiers vs. Logical Layers
• The Standard Layered Stack: Data Access, Business, Presentation
• The "Database-Centric" Mindset
• Testability, Maintainability, Performance
• LAB: Creating a Simple N-Tier Application

Clean Architecture

Clean Architecture tries to keep business logic independent from frameworks and infrastructure. This module explains why this separation makes applications easier to test, change and maintain, while also showing where it can add extra complexity.

• Dependency Inversion
• Domain, Application, Infrastructure, Presentation Layers
• Testability, Maintainability, Performance
• Domain Modelling with Entities and Value Objects
• Domain Services and Application Services
• LAB: Migrating from N-Tier to Clean Architecture

Mapping

Mapping is often used to separate different models in an application, but it is not free. This module explains why mapping exists, what problems it tries to solve, and why too much mapping can slow teams down.

• To DTO or Not?
• The Domain Leakage Problem
• Flattening Objects
• Manual vs. Automated Mapping
• Performance and Projections
• Architectural Purity and Developer Productivity
• LAB: Using Source Generation for Mapping

Persistence Strategy

Data access is a frequent source of design problems in .NET applications. This module evaluates repository patterns, common pitfalls, and practical DbContext usage in both Clean Architecture and Vertical Slices.

• Repository Pattern
• Leaky Abstractions
• The "Generic Repository" Trap
• DbContext as a Repository
• Unit Testing Reality
• Aggregates
• LAB: Using DbContext in Clean Architecture

Vertical Slices

In layered architectures, small changes often touch many parts of the system. This module explains why organizing code around features can make applications easier to understand, change and maintain.

• The Layer "Tax"
• Features over Layers Philosophy
• Abstraction over DRY
• Implementation Details
• Managing Shared Logic
• The Testing Pyramid vs. The Diamond
• Maintainability and Performance
• LAB: Migrating from Clean Architecture to Vertical Slices

Result Objects and Exceptions

Operations can succeed, fail, be cancelled or return different kinds of results. This module dicusses how to handle these situations clearly and consistently, and how these choices affect control flow, clarity and system behavior.

• Return Codes
• Flow Control vs. Error Handling
• Validation
• Running Jobs
• Performance Impact
• Hidden Side Effects
• "Try"-pattern
• Discriminated Unions and "OneOf"
• LAB: Exploring Trade-offs with FluentResults

CQRS

Command Query Responsibility Segregation (CQRS) is a powerful pattern for complex domains, but it can be overkill for simpler applications. This module explains why CQRS exists, what problems it solves, and how to apply it pragmatically without unnecessary complexity.

• CQS
• System-Level CQRS
• Application-Level CQRS
• Commands, Queries and Handlers
• Cross-Cutting Concerns
• LAB: Using CQRS with Vertical Slices

Messaging Patterns

Messaging is often introduced to decouple components, but can easily increase complexity. This module explains why messaging patterns exist and how to apply them deliberately without turning systems into hard-to-follow workflows.

• Request/Reply and Notifications
• Mediator: Hero or Villain?
• Mediator Libraries
• Cross-Cutting Concerns
• Best Practices and Anti-Patterns
• Event Aggregator
• LAB: Implementing Messaging with Mediator

Microservices

By splitting up a monolith into bite-size microservices, you make your application a lot more suitable for the cloud.

• Dealing with Evolution in an Application
• Benefits and Drawbacks
• Communication: client-service, service-service
• Data Isolation
• LAB: Building simple Microservice with Aspire

Modular Monolith

This module explains why modular monoliths offer a pragmatic alternative that enables strong boundaries without premature distribution.

• The Microservices Tax
• Modular Monolith as strategic middle ground
• Module Communication & Integration
• Data Isolation Strategies
• Implementation Risks and Pitfalls
• LAB: Migrating from Clean Architecture to Modular Monolith

Monorepo vs Polyrepo

Repository structure influences dependency management, team autonomy and evolution speed. This module explains why neither monorepos nor polyrepos are universally correct and how context determines their effectiveness.

• Atomic Refactoring
• The "Dependency Hell" Tax
• The "Slow Build" Myth
• Team Ownership
• Private NuGet feeds
• "Shared Library" Dependency Tax
• NuGet Versioning
• Source Mapping

Building Reusable Libraries

Reusable libraries often fail due to hidden assumptions about their consumers. This module explains why designing for unknown usage contexts is essential for adoption, longevity and safe evolution.

• Defensive Visibility
• Exception Safety
• Writing Context-Agnostic Code
• Abstractions Package
• Minimize Dependencies
• Idempotent Registrations
• Maintaining Compatibility
• Postel's Law
• LAB: Building a Reusable Library for Document Processing

Governing Third-Party Libraries

Third-party libraries introduce long-term risk beyond immediate functionality. This module explains why dependency choices are architectural decisions involving security, licensing and sustainability.

• Library Selection Criteria
• Open Source versus Commercial Libraries
• Supply Chain Security

Quality Gates

Quality does not scale through manual reviews alone. This module explains why automated quality gates are needed to enforce standards, protect architecture and keep delivery predictable.

• Code Style and Formatting
• Static Code Analysis Tools
• Complexity Metrics
• Roslyn Analyzers
• Testing & Coverage Thresholds
• Security & Dependency Audits
• Architectural Tests
• AI Code Generation Guidelines
• Acceptance Criteria
• Quality Gates in CI/CD
• LAB: Setting up a Quality Gated Project

Monitoring and Observability

Without observability, systems cannot be trusted in production. This module explains why structured telemetry enables faster diagnosis, better decisions and controlled operational cost.

• Logging vs Telemetry
• Structured Logging in .NET
• Instrumentation and OpenTelemetry
• Application Health and Lifecycle
• Distributed Tracing
• LAB: OpenTelemetry with Aspire

Feature Management

How teams work with branches has a big impact on delivery speed and risk. This module explains why different branching strategies exist, how feature flags enable trunk-based development, and how the same flags can be used to safely release features and control deployments in production.

• Feature Flags
• Branching Strategies: GitFlow vs. Trunk-Based
• Deployment Patterns: Canary, Blue-Green, A/B Testing
• LAB: Targeting Groups with Feature Flags