request/src/request.validation/package-readme.md

Features

• Composable validators: Build validators by inheriting from Validator<T> and defining rules with RuleFor and RuleForEach.
• Built-in and custom rules: Use helpers like NotEmpty, Length, Between, and Matches, or define custom predicates with Must.
• Structured validation output: Each failure is returned as a Problem with a property path, message, severity, code, and attempted value.
• Nested validation: Reuse validators for complex object graphs with SetValidator, including DI-based resolution.

Getting Started

Install the NuGet package:

dotnet add package Geekeey.Request.Validation

You may need to add our NuGet feed to your nuget.config this can be done by running the following command:

dotnet nuget add source -n geekeey https://code.geekeey.de/api/packages/geekeey/nuget/index.json

Usage

using Geekeey.Request.Validation;

public sealed record Address(string? Street);

public sealed record CreateUserRequest(
  string? Name,
  int Age,
  Address? Address,
  IReadOnlyList<string> Tags);

public sealed class AddressValidator : Validator<Address>
{
  public AddressValidator()
  {
    RuleFor(address => address.Street)
      .NotEmpty();
  }
}

public sealed class CreateUserRequestValidator : Validator<CreateUserRequest>
{
  public CreateUserRequestValidator()
  {
    RuleFor(request => request.Name)
      .NotEmpty()
      .Length(2, 100)
      .WithCode("NAME_INVALID");

    RuleFor(request => request.Age)
      .Between(18, 120);

    RuleFor(request => request.Address)
      .SetValidator(new AddressValidator());

    RuleForEach(request => request.Tags)
      .NotEmpty()
      .WithSeverity(Severity.Warning);
  }
}

var validator = new CreateUserRequestValidator();
var validation = validator.Validate(new CreateUserRequest(
  Name: "",
  Age: 16,
  Address: new Address(""),
  Tags: ["", "admin"]));

foreach (var problem in validation.Problems)
{
  Console.WriteLine($"{problem.PropertyPath}: {problem.Message}");
}

The resulting Problem entries include full property paths like Address.Street and Tags[0], making it easy to surface validation errors back to callers or APIs.