creating-cqrs-command

Creating a New CQRS Command

Overview

This skill guides you through creating a new CQRS Command in the Tactic Management API. Commands represent write operations that modify system state (POST, PATCH, DELETE, or state-changing POST operations).

When to use this skill:

• Adding a new POST endpoint that creates or modifies data
• Implementing PATCH operations for updates
• Creating DELETE endpoints
• Adding business logic that changes tactic status or state
• Implementing any operation that writes to the database

Architecture Context:

• Pattern: CQRS (Command Query Responsibility Segregation) with MediatR
• Stack: .NET 8, Entity Framework Core, FluentValidation
• Layers: API → Application → Domain → Infrastructure
• Testing: BDD/GWT pattern with xUnit

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Complete Implementation Checklist

Phase 1: Define Domain Models

1.1 Create Command Class

Location: src/api/src/TacticManagement.Application/Tactics/Commands/

Commands use the record pattern and implement IRequest<TResponse>:

using MediatR;
using TacticManagement.Application.Tactics.DTOs;

namespace TacticManagement.Application.Tactics.Commands;

/// <summary>
/// Command to [describe what this command does].
/// The handler will [describe key responsibilities].
/// </summary>
public record YourCommand(
    Guid TacticId,
    string UserId,
    // Add other parameters as needed
    YourRequest Request
) : IRequest<YourResponse>;

Naming Convention:

• Pattern: {Verb}{Noun}Command (e.g., CreateTacticCommand, MarkTacticProofReadyCommand)
• Use descriptive verbs: Create, Update, Delete, Mark, Submit, Approve, Reject, Request, Complete
• Always include UserId for audit trail
• Include TacticId if operating on existing entity

File Organization:

• Simple commands: Single file YourCommand.cs
• Complex commands: Folder with YourCommand.cs, YourCommandHandler.cs, YourCommandValidator.cs

1.2 Create Request DTO (if needed)

Location: src/api/src/TacticManagement.Application/Tactics/Commands/