RGamaFelix.CqrsDispatcher.Validator 4.0.0

RGamaFelix.CqrsDispatcher.Validator

A FluentValidation integration for the RGamaFelix.CqrsDispatcher framework. This package provides automatic validation for commands and queries using the pipeline behavior pattern.

Prerequisites

• RGamaFelix.CqrsDispatcher (Core project)
• FluentValidation

Installation

Add the validator project to your solution and ensure it references the core RGamaFelix.CqrsDispatcher project.

# Using dotnet CLI
dotnet add package RGamaFelix.CqrsDispatcher.Validator

Configuration

To enable automatic validation, register the validator extensions in your Program.cs or Startup.cs:

using RGamaFelix.CqrsDispatcher.Validator.Configuration;

// ... in your ServiceCollection setup
services.AddCqrsDispatcherFramework(); // Base dispatcher
services.RegisterCqrsDispatcherValidator(); // This package's validation pipeline

You also need to register your FluentValidation validators. The dispatcher will automatically pick up any IValidator<T> registered in the DI container for your request types.

using FluentValidation;

// Register all validators from an assembly
services.AddValidatorsFromAssemblyContaining<MyCommandValidator>();

Usage Example

1. Define your Request and Validator

using FluentValidation;
using RGamaFelix.CqrsDispatcher.Command;

public record CreateUserCommand(string Username, string Email) : ICommandRequest;

public class CreateUserValidator : AbstractValidator<CreateUserCommand>
{
    public CreateUserValidator()
    {
        RuleFor(x => x.Username).NotEmpty().MinimumLength(3);
        RuleFor(x => x.Email).NotEmpty().EmailAddress();
    }
}

2. Dispatch and Handle Validation Errors

When you dispatch a command or query, the CommandRequestValidator or QueryRequestValidator will intercept the request, run all registered validators, and throw a FluentValidation.ValidationException if any validation fails.

try 
{
    var command = new CreateUserCommand("", "invalid-email");
    await _dispatcher.PublishAsync(command);
}
catch (ValidationException ex) 
{
    // Handle validation failures (e.g., return 400 Bad Request)
    foreach (var error in ex.Errors)
    {
        Console.WriteLine($"{error.PropertyName}: {error.ErrorMessage}");
    }
}

Features

• Automatic Pipeline Integration: Plugs into the CQRS dispatcher pipeline without manual calls to Validate().
• Supports Multiple Validators: Runs all registered validators for a specific request type.
• Async Validation: Uses FluentValidation's ValidateAsync for non-blocking validation.
• Transparent Execution: If no validators are registered for a type, the pipeline continues normally.