Getting Started

Installation

Add the core library to your project. The integration and testing packages are optional.

Core library (required)

dotnet add package ZeroAlloc.Validation

ASP.NET Core auto-validation (optional)

dotnet add package ZeroAlloc.Validation.AspNetCore

Test assertion helpers (optional)

dotnet add package ZeroAlloc.Validation.Testing

How it works

ZeroAlloc.Validation uses a Roslyn source generator that runs at compile time, not at runtime. It inspects your annotated models and emits a concrete validator class (e.g. RegisterUserRequestValidator) that extends ValidatorFor<T>. No reflection, no expression trees — pure IL at build time. The result has no allocations on the hot path.

Annotate your model

Apply [Validate] to a class, then annotate each property with the constraint attributes you need:

using ZeroAlloc.Validation;

[Validate]
public class RegisterUserRequest
{
    [NotEmpty][MaxLength(100)] public string Username { get; set; } = "";
    [NotEmpty][MinLength(8)]   public string Password { get; set; } = "";
    [NotEmpty][EmailAddress]   public string Email    { get; set; } = "";
}

The generator emits RegisterUserRequestValidator in the same namespace as your model. For flat models like this one (no nested validated properties), the generated validator has a parameterless constructor.

Call the validator

Instantiate the generated validator and call Validate. The returned ValidationResult exposes IsValid and a zero-allocation Failures span:

var validator = new RegisterUserRequestValidator();

var result = validator.Validate(new RegisterUserRequest
{
    Username = "",
    Password = "abc",
    Email    = "not-an-email"
});

Console.WriteLine(result.IsValid); // false

foreach (ref readonly var failure in result.Failures)
    Console.WriteLine($"[{failure.PropertyName}] {failure.ErrorMessage}");
// [Username] 'Username' must not be empty.
// [Password] 'Password' must be at least 8 characters.
// [Email] 'Email' is not a valid email address.

Each ValidationFailure carries:

• PropertyName — the name of the property that failed
• ErrorMessage — a human-readable description of the failure
• ErrorCode — an optional machine-readable code
• Severity — Error, Warning, or Info

Next steps

• Attribute Reference — all 25+ built-in attributes
• Nested Validation — validating nested objects
• Collection Validation — validating lists and arrays
• ASP.NET Core Integration — auto-validation in controllers