AdaskoTheBeAsT.FluentValidation.SimpleInjector

Seamlessly integrate FluentValidation with SimpleInjector - automatic validator registration made simple.

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Why Use This?

Stop manually registering validators one by one. This library automatically scans your assemblies and registers all IValidator<T> implementations with SimpleInjector, saving you time and reducing boilerplate code.

Key Features

• Zero Configuration - Works out of the box with sensible defaults
• Flexible Scanning - Register validators by assembly, marker types, or custom configuration
• Lifecycle Control - Choose between Singleton, Scoped, or Transient lifestyles
• Smart Registration - Supports both single validator and collection patterns
• Selective Registration - Skip specific validators with [SkipValidatorRegistration] attribute
• Multi-Target Support - Compatible with .NET 8.0, 9.0, and 10.0

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Installation

dotnet add package AdaskoTheBeAsT.FluentValidation.SimpleInjector

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Quick Start

Basic Usage

The simplest way to register all validators from an assembly:

using SimpleInjector;
using AdaskoTheBeAsT.FluentValidation.SimpleInjector;

var container = new Container();

// Register all validators from the assembly containing PersonValidator
container.AddFluentValidation(typeof(PersonValidator));

That's it! All validators in that assembly are now registered and ready to use.

Resolve and Use

var validator = container.GetInstance<IValidator<Person>>();
var result = validator.Validate(new Person { Name = "John" });

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Usage Patterns

1. Register by Marker Types

Use types as markers to identify which assemblies to scan:

// Single assembly
container.AddFluentValidation(typeof(PersonValidator));

// Multiple assemblies
container.AddFluentValidation(
    typeof(PersonValidator),
    typeof(OrderValidator),
    typeof(ProductValidator)
);

2. Register by Assemblies

Directly specify assemblies to scan:

var assembly = typeof(PersonValidator).Assembly;
container.AddFluentValidation(assembly);

// Or multiple assemblies
var assemblies = new[] 
{ 
    typeof(PersonValidator).Assembly,
    typeof(OrderValidator).Assembly 
};
container.AddFluentValidation(assemblies);

3. Scan Solution Assemblies

Automatically discover and register validators from all assemblies in your solution:

public static class ValidatorConfig
{
    public static void RegisterValidators(Container container)
    {
        var assemblies = AppDomain.CurrentDomain
            .GetAssemblies()
            .Where(a => a.FullName.StartsWith("YourCompany."))
            .ToList();

        container.AddFluentValidation(assemblies);
    }
}

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Advanced Configuration

Lifecycle Management

Choose how validators are instantiated and cached:

// Singleton (default) - one instance shared across the application
container.AddFluentValidation(cfg => 
{
    cfg.WithAssembliesToScan(assemblies);
    cfg.AsSingleton();
});

// Scoped - one instance per scope/request
container.AddFluentValidation(cfg => 
{
    cfg.WithAssembliesToScan(assemblies);
    cfg.AsScoped();
});

// Transient - new instance every time
container.AddFluentValidation(cfg => 
{
    cfg.WithAssembliesToScan(assemblies);
    cfg.AsTransient();
});

Registration Patterns

Single Validator Pattern (Default)

Registers one validator per type. Use this when you have one validator per model:

container.AddFluentValidation(cfg =>
{
    cfg.WithAssembliesToScan(assemblies);
    cfg.RegisterAsSingleValidator(); // Default
});

// Resolves to a single IValidator<Person>
var validator = container.GetInstance<IValidator<Person>>();

Validator Collection Pattern

Register multiple validators for the same type:

container.AddFluentValidation(cfg =>
{
    cfg.WithAssembliesToScan(assemblies);
    cfg.RegisterAsValidatorCollection();
});

// Resolves to multiple validators
var validators = container.GetAllInstances<IValidator<Person>>();

Selective Registration

Skip specific validators from auto-registration:

using AdaskoTheBeAsT.FluentValidation.SimpleInjector;

// This validator will be excluded from registration
[SkipValidatorRegistration]
public class PersonInternalValidator : AbstractValidator<Person>
{
    public PersonInternalValidator()
    {
        RuleFor(x => x.Name).NotEmpty();
    }
}

Use Case: When building composite validators using included rules:

public class PersonValidator : AbstractValidator<Person>
{
    public PersonValidator()
    {
        Include(new PersonInternalValidator());
        Include(new PersonExternalValidator());
    }
}

// Mark the included validators to prevent duplicate registration
[SkipValidatorRegistration]
public class PersonInternalValidator : AbstractValidator<Person> { ... }

[SkipValidatorRegistration]
public class PersonExternalValidator : AbstractValidator<Person> { ... }

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Complete Configuration Example

using SimpleInjector;
using AdaskoTheBeAsT.FluentValidation.SimpleInjector;

public class Startup
{
    public void ConfigureServices()
    {
        var container = new Container();

        // Advanced configuration
        container.AddFluentValidation(cfg =>
        {
            // Specify assemblies to scan
            cfg.WithAssembliesToScan(
                typeof(PersonValidator).Assembly,
                typeof(OrderValidator).Assembly
            );

            // Set validator lifecycle
            cfg.AsScoped();

            // Use single validator pattern
            cfg.RegisterAsSingleValidator();
        });

        // Verify container configuration
        container.Verify();
    }
}

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Real-World Examples

ASP.NET Core Integration

public class Program
{
    public static void Main(string[] args)
    {
        var builder = WebApplication.CreateBuilder(args);

        // Add SimpleInjector
        builder.Services.AddSimpleInjector(container =>
        {
            // Register validators with scoped lifetime
            container.AddFluentValidation(cfg =>
            {
                cfg.WithAssembliesToScan(typeof(Program).Assembly);
                cfg.AsScoped();
            });
        });

        var app = builder.Build();
        app.Run();
    }
}

MediatR Pipeline Integration

// Validation pipeline behavior
public class ValidationBehavior<TRequest, TResponse> 
    : IPipelineBehavior<TRequest, TResponse>
    where TRequest : IRequest<TResponse>
{
    private readonly IValidator<TRequest> _validator;

    public ValidationBehavior(IValidator<TRequest> validator)
    {
        _validator = validator;
    }

    public async Task<TResponse> Handle(
        TRequest request, 
        RequestHandlerDelegate<TResponse> next, 
        CancellationToken cancellationToken)
    {
        var validationResult = await _validator.ValidateAsync(request, cancellationToken);
        
        if (!validationResult.IsValid)
        {
            throw new ValidationException(validationResult.Errors);
        }

        return await next();
    }
}

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Framework Support

.NET Version	Support
.NET 10.0	✅
.NET 9.0	✅
.NET 8.0	✅

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Dependencies

• FluentValidation >= 12.1.0
• SimpleInjector >= 5.5.0

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Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

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License

This project is licensed under the MIT License - see the LICENSE file for details.

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Author

Adam "AdaskoTheBeAsT" Pluciński

If this library saved you time, consider giving it a ⭐ on GitHub!