SharpGrip FluentValidation AutoValidation

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Introduction

SharpGrip FluentValidation AutoValidation is an extension of the FluentValidation (v10+) library enabling automatic asynchronous validation in MVC controllers and minimal APIs (endpoints). The library FluentValidation.AspNetCore is no longer being maintained and is unsupported. As a result, support for automatic validation provided by this library is no longer available. This library re-introduces this functionality for MVC controllers and introduces automatic validation for minimal APIs (endpoints). It enables developers to easily implement automatic validation in their projects.

Installation

Validator registration

To enable this library to automatically resolve and invoke validators for your models, you must register your validators with the Dependency Injection (DI) service container.

Manual registration

Manually register your validator with the service container:

services.AddScoped<IValidator<User>, UserValidator>();

Automatic registration

Automatically register all validators from the assembly containing your UserValidator:

services.AddValidatorsFromAssemblyContaining<UserValidator>();

For more instructions on setting that up please see https://docs.fluentvalidation.net/en/latest/di.html.

MVC controllers

For MVC controllers reference NuGet package SharpGrip.FluentValidation.AutoValidation.Mvc (https://www.nuget.org/packages/SharpGrip.FluentValidation.AutoValidation.Mvc).

using SharpGrip.FluentValidation.AutoValidation.Mvc.Extensions;

builder.Services.AddFluentValidationAutoValidation();

Minimal APIs (endpoints)

For minimal APIs (endpoints) reference NuGet package SharpGrip.FluentValidation.AutoValidation.Endpoints (https://www.nuget.org/packages/SharpGrip.FluentValidation.AutoValidation.Endpoints).

Enabling minimal API (endpoint) automatic validation can be done on both route groups and routes.

using SharpGrip.FluentValidation.AutoValidation.Endpoints.Extensions;

builder.Services.AddFluentValidationAutoValidation();

var app = builder.Build();
var endpointGroup = app.MapGroup("/some-group").AddFluentValidationAutoValidation();
endpointGroup.MapPost("/", (SomeModel someModel) => $"Hello {someModel.Name}");

app.MapPost("/", (SomeOtherModel someOtherModel) => $"Hello again {someOtherModel.Name}").AddFluentValidationAutoValidation();

Configuration

MVC controllers

Property	Default value	Description
DisableBuiltInModelValidation	false	Disables the built-in .NET model (data annotations) validation.
ValidationStrategy	ValidationStrategy.All	Configures the validation strategy. Validation strategy ValidationStrategy.All enables asynchronous automatic validation on all controllers. Validation strategy ValidationStrategy.Annotations enables asynchronous automatic validation on controllers decorated (class or method) with a [AutoValidationAttribute] attribute.
EnableBodyBindingSourceAutomaticValidation	true	Enables asynchronous automatic validation for parameters bound from BindingSource.Body binding sources (typically parameters decorated with the [FromBody] attribute).
EnableFormBindingSourceAutomaticValidation	true	Enables asynchronous automatic validation for parameters bound from BindingSource.Form binding sources (typically parameters decorated with the [FromForm] attribute).
EnableQueryBindingSourceAutomaticValidation	true	Enables asynchronous automatic validation for parameters bound from BindingSource.Query binding sources (typically parameters decorated with the [FromQuery] attribute).
EnablePathBindingSourceAutomaticValidation	true	Enables asynchronous automatic validation for parameters bound from BindingSource.Path binding sources (typically parameters decorated with the [FromRoute] attribute).
EnableHeaderBindingSourceAutomaticValidation	false	Enables asynchronous automatic validation for parameters bound from BindingSource.Header binding sources (typically parameters decorated with the [FromHeader] attribute).
EnableCustomBindingSourceAutomaticValidation	false	Enables asynchronous automatic validation for parameters bound from BindingSource.Custom binding sources.
EnableNullBindingSourceAutomaticValidation	false	Enables asynchronous automatic validation for parameters not bound from any binding source (typically parameters without a declared or inferred binding source).

using SharpGrip.FluentValidation.AutoValidation.Mvc.Extensions;

builder.Services.AddFluentValidationAutoValidation(configuration =>
{
    // Disable the built-in .NET model (data annotations) validation.
    configuration.DisableBuiltInModelValidation = true;

    // Only validate controllers decorated with the `AutoValidation` attribute.
    configuration.ValidationStrategy = ValidationStrategy.Annotations;

    // Enable validation for parameters bound from `BindingSource.Body` binding sources.
    configuration.EnableBodyBindingSourceAutomaticValidation = true;

    // Enable validation for parameters bound from `BindingSource.Form` binding sources.
    configuration.EnableFormBindingSourceAutomaticValidation = true;

    // Enable validation for parameters bound from `BindingSource.Query` binding sources.
    configuration.EnableQueryBindingSourceAutomaticValidation = true;

    // Enable validation for parameters bound from `BindingSource.Path` binding sources.
    configuration.EnablePathBindingSourceAutomaticValidation = true;

    // Enable validation for parameters bound from 'BindingSource.Custom' binding sources.
    configuration.EnableCustomBindingSourceAutomaticValidation = true;

    // Replace the default result factory with a custom implementation.
    configuration.OverrideDefaultResultFactoryWith<CustomResultFactory>();
});

public class CustomResultFactory : IFluentValidationAutoValidationResultFactory
{
    public Task<IActionResult?> CreateActionResult(ActionExecutingContext context, ValidationProblemDetails validationProblemDetails, IDictionary<IValidationContext, ValidationResult> validationResults)
    {
        return new BadRequestObjectResult(new {Title = "Validation errors", ValidationErrors = validationProblemDetails?.Errors});
    }
}

Minimal APIs (endpoints)

using SharpGrip.FluentValidation.AutoValidation.Endpoints.Extensions;

builder.Services.AddFluentValidationAutoValidation(configuration =>
{
    // Replace the default result factory with a custom implementation.
    configuration.OverrideDefaultResultFactoryWith<CustomResultFactory>();
});

public class CustomResultFactory : IFluentValidationAutoValidationResultFactory
{
    public IResult CreateResult(EndpointFilterInvocationContext context, ValidationResult validationResult)
    {
        var validationProblemErrors = validationResult.ToValidationProblemErrors();

        return Results.ValidationProblem(validationProblemErrors, "Some details text.", "Some instance text.", (int) HttpStatusCode.BadRequest, "Some title.");
    }
}

Validation attributes

MVC controllers

Customizing automatic validation behavior is achievable through the use of attributes.

The [AutoValidateAlways] attribute can be applied to a controller parameter, compelling automatic validation to disregard the validation check for a valid binding source. This proves useful when the ApiBehaviorOptions.SuppressInferBindingSourcesForParameters option is enabled, and a custom model is used, with parameters bound from multiple binding sources.

The [AutoValidateNever] attribute can be placed on a controller class, controller method, or controller parameter, instructing automatic validation to be skipped.

Validation interceptors

Note: Using validation interceptors is considered to be an advanced feature and is not needed for most use cases.

Validation interceptors provide a mechanism for intercepting and modifying the validation process. This can be achieved through two distinct approaches:

Global validation interceptor: Create a custom class that implements the IGlobalValidationInterceptor interface and register it with the service provider.

Per validator interceptor: Implement the IValidatorInterceptor interface directly on a specific validator.

In the validation process, both the global and the validator interceptors are resolved and invoked (if they exist), thereby establishing a miniature pipeline of validation interceptors:

IValidatorInterceptor.BeforeValidation()
IGlobalValidationInterceptor.BeforeValidation()

>> Validation <<

IValidatorInterceptor.AfterValidation()
IGlobalValidationInterceptor.AfterValidation()

Both interfaces define a BeforeValidation and a AfterValidation method.

The BeforeValidation method gets called before validation and allows you to return a custom IValidationContext which gets passed to the validator. In case you return null the default IValidationContext will be passed to the validator.

The AfterValidation method gets called after validation and allows you to return a custom IValidationResult which gets passed to the IFluentValidationAutoValidationResultFactory. In case you return null the existing ValidationResult will be passed to the IFluentValidationAutoValidationResultFactory.

MVC controllers

// Example of a global validation interceptor.
builder.Services.AddTransient<IGlobalValidationInterceptor, CustomGlobalValidationInterceptor>();

public class CustomGlobalValidationInterceptor : IGlobalValidationInterceptor
{
    public Task<IValidationContext?> BeforeValidation(ActionExecutingContext actionExecutingContext, IValidationContext validationContext, CancellationToken cancellationToken = default)
    {
        // Return a custom `IValidationContext` or null.
        return Task.FromResult<IValidationContext?>(null);
    }

    public Task<ValidationResult?> AfterValidation(ActionExecutingContext actionExecutingContext, IValidationContext validationContext, ValidationResult validationResult, CancellationToken cancellationToken = default)
    {
        // Return a custom `ValidationResult` or null.
        return Task.FromResult<ValidationResult?>(null);
    }
}

// Example of a single validator interceptor.
private class TestValidator : AbstractValidator<TestModel>, IValidatorInterceptor
{
    public TestValidator()
    {
        RuleFor(x => x.Parameter1).Empty();
        RuleFor(x => x.Parameter2).Empty();
        RuleFor(x => x.Parameter3).Empty();
    }

    public Task<IValidationContext?> BeforeValidation(ActionExecutingContext actionExecutingContext, IValidationContext validationContext, CancellationToken cancellationToken = default)
    {
        // Return a custom `IValidationContext` or null.
        return Task.FromResult<IValidationContext?>(null);
    }

    public Task<ValidationResult?> AfterValidation(ActionExecutingContext actionExecutingContext, IValidationContext validationContext, ValidationResult validationResult, CancellationToken cancellationToken = default)
    {
        // Return a custom `ValidationResult` or null.
        return Task.FromResult<ValidationResult?>(null);
    }
}

Minimal APIs (endpoints)

// Example of a global validation interceptor.
builder.Services.AddTransient<IGlobalValidationInterceptor, CustomGlobalValidationInterceptor>();

public class CustomGlobalValidationInterceptor : IGlobalValidationInterceptor
{
    public Task<IValidationContext?> BeforeValidation(EndpointFilterInvocationContext endpointFilterInvocationContext, IValidationContext validationContext, CancellationToken cancellationToken = default)
    {
        // Return a custom `IValidationContext` or null.
        return Task.FromResult<IValidationContext?>(null);
    }

    public Task<ValidationResult?> AfterValidation(EndpointFilterInvocationContext endpointFilterInvocationContext, IValidationContext validationContext, ValidationResult validationResult, CancellationToken cancellationToken = default)
    {
        // Return a custom `ValidationResult` or null.
        return Task.FromResult<ValidationResult?>(null);
    }
}

// Example of a single validator interceptor.
private class TestValidator : AbstractValidator<TestModel>, IValidatorInterceptor
{
    public TestValidator()
    {
        RuleFor(x => x.Parameter1).Empty();
        RuleFor(x => x.Parameter2).Empty();
        RuleFor(x => x.Parameter3).Empty();
    }

    public Task<IValidationContext?> BeforeValidation(EndpointFilterInvocationContext endpointFilterInvocationContext, IValidationContext validationContext, CancellationToken cancellationToken = default)
    {
        // Return a custom `IValidationContext` or null.
        return Task.FromResult<IValidationContext?>(null);
    }

    public Task<ValidationResult?> AfterValidation(EndpointFilterInvocationContext endpointFilterInvocationContext, IValidationContext validationContext, ValidationResult validationResult, CancellationToken cancellationToken = default)
    {
        // Return a custom `ValidationResult` or null.
        return Task.FromResult<ValidationResult?>(null);
    }
}