• Concepts
  • Value Validator
  • State Validator
  • Validation Error Format
• Valigator Packages
  • Valigator.Core
  • Valigator.AspNetCore
• Usage
• Random Things To Move to Better Places
  • Custom Validations
• Gotchas

Valigator is .NET suite of libraries that enabled the declaration of complex validation rules directly on model properties.

Valigator.AspNetCore provides a JsonConverter and attaches to the AspNetCore deserialization process.

Any model to be validated by Valigator must have the [ValigatorModel] attribute. This will result in any property decorated by the Data<T> being validated by the converter.

Usage of the Data<T> decorator is governed by a few rules:

• All properties must have a declared setter. This setter may be private.

• Data must be one of Required, Optional, or Defaulted

  • Required
    • A value must be provided.
    • If a value is not provided, an error is produced.
    • Whether this is nullable or not is dictated by nullability (See XXXXX below).
    • This value is stored in Data<T>
    • Example:

    Data<int> RequiredInt { get; set; } = Data.Required<int>().GreaterThan(1);

  • Optional
    • A value does not need to be provided.
    • If a vlaue is not provided, Option.None<T> is produced.
    • Whether this is nullable or not is dictated by nullability (See XXXXX below).
    • This value is stored in Data<Option<T>>
    • Example:

    Data<Option<int>> OptionalInt { get; set; } = Data.Optional<int>().GreaterThan(1);

  • Defaulted
    • A value does not need to be provided.
    • When a value is not provided, a default value is used instead.
    • Whether this is nullable or not is dictated by nullability (See XXXXX below).
    • This value is stored in Data<T>
    • Example:

    public Data<int> DefaultedInt { get; set; } = Data.Defaulted<int>(3).GreaterThan(1);

• Nullability means that null is a valid input value

  • Nullable value are indicated by adding Nullable().
    • Nullable Required means that a value must be provided, but it can be null.
    • Nullable Optional means that a value does not need to be provided, but if it is, it may be null.
    • Nullable Default means that a value does not need to be provided, but if it is, it may be null.
  • Nullable implies Option<T>
  • A nullable collection means that the collection itself may be null
  • TODO: Items Nullable Information
  • Examples:

  public Data<Option<int>> NullableRequiredInt { get; set; } = Data.Required<int>().Nullable().GreaterThan(1);

• Collections are defined slightly differently than regular Data fields.

  public Data<int[]> RequiredIntegerCollection { get; set; } = Data.Collection<int>(x => x.GreaterThan(1)).Required();
  
  public Data<int[]> DefaultedIntegerCollection { get; set; } = Data.Collection<int>(x => x.GreaterThan(1)).Defaulted(new[]{1, 2, 3});
  
  public Data<int[]> DefaultEmptyIntegerCollection { get; set; } = Data.Collection<int>(x => x.GreaterThan(1)).DefaultedToEmpty();
  
  public Data<Option<int[]>> OptionalIntegerCollection { get; set; } = Data.Collection<int>(x => x.GreaterThan(1)).Optional();

• Validating Non-Data Fields Apply the [ValidateContents] attribute to the property or field to be validated. This will cause Valigator to run validations upon whatever object is contained in this field or property.

  Example:

  [ValidateContents]
  private readonly object _value;

• Any anonymous type with Valigator properties (properties of type Data<T>) must be converted to a ValigatorModel<T>. The easiest way to do this is to use the .ToValigatorModel() extension method from Valigator.Newtonsoft.Json.

  new { Type = "A Type", UnitCost = Data.Require<int>() }.ToValigatorModel()

When a Valigator model is deserialized, it deserializes into one of two states:

• Set - Data was provided and passes all validations
• Unset - No data was provided. This is equivalent to skipping a field. Passing in null is not Unset, that is either Valid or Invalid.

The core library of Valigator.

Library specifically to make adding to an AspNetCore application easy.

• Install the appropriate Valigator packages from the list above.
• In configure Valigator service

  public void ConfigureServices(IServiceCollection services)
  {
      services
          .AddValigator(InputErrorHandler, OutputErrorHandler);
  }

• Add the input error handler. This handler will be run when a validation error occurs deserializing into the object.

  private IActionResult InputErrorHandler(Valigator.ValidationError[] errors)
      => errors.ToUnexpectedError().ToActionResult();

• Add the output error handler. This handler will be run when a validation error occurs serializing objects.

  private IActionResult OutputErrorHandler(ModelError[] errors)
      => errors.ToValidationError().ToActionResult();

Examples:

public Data<Option<int>> IntegerValue { get; set; } = Data.Required<int>().Nullable().Assert("A meaningful description", value => value > 1)

1. All properties must have a setter. This setter may be private.