Ling.FluentValidation.Annotations 1.0.0-preview.2

Ling.FluentValidation.Annotations

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Ling.FluentValidation.Annotations contains the declaration-only API for marking DTOs and describing validation rules. It does not depend on FluentValidation, so shared Contracts projects do not acquire a validation-runtime dependency.

The package also includes Roslyn analyzers and code fixes that report invalid rule usage while editing and building.

Installation

Install the package in the project that owns request and DTO types:

dotnet add package Ling.FluentValidation.Annotations --prerelease

Declare a validation contract

Generation is explicit. A type with rules must be marked with [GenerateValidator]:

using Ling.FluentValidation.Annotations;

namespace MyApplication.Contracts;

[GenerateValidator]
public sealed record CreateOrderRequest
{
    [NotEmpty]
    [Length(3, 100)]
    public string Name { get; init; } = string.Empty;

    [InclusiveBetween(1, 100)]
    public int Quantity { get; init; }
}

The analyzer reports rules placed on an unmarked type and offers a code fix that adds [GenerateValidator].

Rules

Annotations cover value-based, type-independent rules, including:

• null and empty checks;
• length and regular-expression checks;
• equality, ordering, and inclusive or exclusive ranges;
• allowed and denied values;
• email, phone, URL, credit card, Base64, file extension, enum, and enum-name checks.

Standard System.ComponentModel.DataAnnotations validation attributes are also recognized by the generator. Rule-specific error messages, codes, severity, display names, and supported conditional members can be configured on Ling attributes.

Rules that depend on services, another validator, or application behavior belong in a partial validator in the receiving project rather than in the contract assembly.

Select a source assembly

The project that receives generated validators explicitly selects external contract assemblies:

using Ling.FluentValidation.Annotations;
using MyApplication.Contracts;

[assembly: GenerateValidatorsFromAssemblyContaining(typeof(CreateOrderRequest))]

On .NET 7 or later, the generic form can be used to omit typeof:

[assembly: GenerateValidatorsFromAssemblyContaining<CreateOrderRequest>]

Configure generated validators

Apply options to the receiving assembly:

[assembly: ValidatorGenerationOptions(
    Namespace = "MyApplication.Validation",
    Visibility = GeneratedValidatorVisibility.Public,
    IsSealed = true,
    ClassLevelCascadeMode = ValidationCascadeMode.Continue,
    RuleLevelCascadeMode = ValidationCascadeMode.Stop)]

Target frameworks

• netstandard2.0 provides the base declaration API.
• net7.0 adds generic attribute forms that only simplify typeof syntax.

Newer applications automatically select the compatible asset.

Related packages

• Ling.FluentValidation provides the source generator, runtime rule implementations, and FluentValidation integration.

License

MIT