ASP.NET Request Validation

Validates request models through attributes, fluent rules, or both. Failures are collected per field and returned as a single 422 response with localized messages, so a client sees every problem at once rather than one at a time.

Works with MVC controllers and minimal API endpoints, discovering rules once at startup and caching them so validation costs a dictionary lookup rather than a reflection pass per request.

Categories

• Localization — where validation messages come from and how keys are named.
• Fluent Validation — declaring rules in code instead of attributes.
• Custom Rules — writing a rule with its own dependencies.
• Extensions — registration and pipeline setup.
• Validation Rules — the full rule catalogue, grouped by family.
• Services — reading the declared rules at runtime.
• Utilities — returning a validation failure from a controller action.
• Types — how a comparison rule reads its target.
• Records — the response shapes.

Quick Example

Program.cs

using AlmightyShogun.AspNet.Core;
using AlmightyShogun.AspNet.Localization;
using AlmightyShogun.AspNet.RequestValidation;

builder.Services
    .AddMessageLocalization(builder.Configuration)
    .AddHttpErrorResponseWriter()
    .AddExceptionHandling()
    .AddAspNetValidation();

builder.Services.AddControllers();

WebApplication app = builder.Build();

app.UseHttpErrorResponses();
app.UseAspNetValidation();
app.MapControllers();

SignupController.cs

using Microsoft.AspNetCore.Mvc;
using AlmightyShogun.AspNet.RequestValidation;

[ApiController]
[Route("signup")]
public sealed class SignupController : ControllerBase
{
    [HttpPost]
    public IActionResult Post(SignupRequest request) => Ok();
}

SignupRequest.cs

using AlmightyShogun.AspNet.RequestValidation;

public sealed record SignupRequest
{
    [Required]
    [Email]
    public string Email { get; init; } = "";

    [Required]
    [Min(12)]
    public string Password { get; init; } = "";

    [RequiredWith(nameof(Password))]
    public string PasswordConfirmation { get; init; } = "";
}