Folder discipline, vertical slices, without the cargo cult.

CQRS in .NET — Practical Guide 2026

CQRS separates write operations (Commands) from read operations (Queries). At its simplest it is a folder discipline: Commands/ and Queries/ instead of one ServiceLayer. Commands change state and return void or an ID. Queries return read models and must have no side effects. MediatR is popular but not required. Vertical Slice Architecture takes CQRS further by co-locating all code for one feature (handler, validator, endpoint, DTO) in a single file/folder.

Interactive Pipeline Flow

FoundationCore LogicProduction

🌐 API Layer — endpoint / controller

Endpoints receive HTTP requests and dispatch a Command or Query — they contain no business logic.

Architecture Diagrams

Vertical Slice Architecture: one folder per feature, all layers co-located.

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Key Design Decisions

📁CQRS is a folder discipline first

Split into Commands/ and Queries/. You don't need MediatR or two databases for CQRS to pay dividends.

🚫No side effects in Query handlers

A Query handler must never write to the database. Queries are safe to retry, cache, and parallel-execute.

🍕Vertical slices over layers

Co-locate endpoint + command + handler + validator in features/FeatureName/. This beats the horizontal layers (Controllers/, Services/, Repos/) anti-pattern.

Discussion