Tolitech.Application.Validation 1.0.0-preview.6

Tolitech.Application.Validation

Overview

Tolitech.Application.Validation is a .NET library that provides a pipeline behavior for MediatR, enabling automatic validation of requests using FluentValidation before they reach their handlers. It helps enforce business rules, improve code quality, and maintain a clean architecture.

Features

• ValidationBehavior: Pipeline behavior for MediatR that validates requests using registered FluentValidation validators.
• Error Aggregation: Collects validation errors and returns them in a standardized result format.
• Integration with Tolitech.Results: Returns validation errors using the Result type for consistency.
• Localization Support: Error messages can be localized using resource files.
• Extensibility: Easily add custom validators for any request type.

Main Class

ValidationBehavior<TRequest, TResponse>

Validates requests before passing them to the next handler.

public sealed class ValidationBehavior<TRequest, TResponse>(IEnumerable<IValidator<TRequest>> validators)
    : IPipelineBehavior<TRequest, TResponse>
    where TRequest : IRequest<TResponse>
    where TResponse : Result

Example Usage

1. Define a Request and Validator

public class CreateOrderCommand : IRequest<Result>
{
    public string ProductId { get; set; }
    public int Quantity { get; set; }
}

public class CreateOrderCommandValidator : AbstractValidator<CreateOrderCommand>
{
    public CreateOrderCommandValidator()
    {
        RuleFor(x => x.ProductId).NotEmpty();
        RuleFor(x => x.Quantity).GreaterThan(0);
    }
}

2. Register Validators and Pipeline Behavior

services.AddValidatorsFromAssemblyContaining<CreateOrderCommandValidator>();
services.AddTransient(typeof(IPipelineBehavior<,>), typeof(ValidationBehavior<,>));

3. Using MediatR

var result = await mediator.Send(new CreateOrderCommand { ProductId = "A1", Quantity = 0 });
if (!result.IsValid)
{
    // Handle validation errors
    foreach (var error in result.Errors)
    {
        Console.WriteLine($"{error.Key}: {error.Message}");
    }
}

Integration Steps

1. Reference Tolitech.Application.Validation in your project.
2. Create FluentValidation validators for your requests.
3. Register validators and ValidationBehavior in your DI container.
4. Use MediatR to send requests; validation will be automatic.

Summary

Tolitech.Application.Validation automates request validation in MediatR pipelines, improving reliability and maintainability in .NET applications.