Question

I’m working in a content development scenario where entities are likely to be created in an incomplete state and remain incomplete for some time. The workflow involved is extremely ad-hoc, preventing me from using a more structured DDD approach.

I have a set of validation rules which must be satisfied at all times, and a further set of validation rules which must be satisfied before an entity is “complete”.

I’m already using the built-in ASP.NET MVC validation to validate the former. What approaches could I use to capture the latter?

For example:-

public class Foo
{
  public int Id { get; set; }

  public virtual ICollection<Bar> Bars { get; set; }
}

public class Bar
{
  public int Id { get; set; }

  [Required] // A Bar must be owned by a Foo at all times
  public int FooId { get; set; }
  public virtual Foo Foo { get; set; }

  [Required] // A Bar must have a working title at all times
  public string WorkingTitle { get; set; }

  public bool IsComplete { get; set; }

  // Cannot use RequiredAttribute on Description as the
  // entity is very likely to be created without one,
  // however a Description is required before the entity
  // can be marked as "IsComplete"
  public string Description { get; set; }
}

Answer 1

There are different approaches you could use:

• Have your model implement the IValidatableObject interface and perform conditional validation without using data annotations.
• Write a custom validation attribute that will perform the conditional validation logic of the Description property based on the value of the IsComplete property.
• Use Mvc Foolproof which already has the RequiredIf validation attribute defined for you so that you don’t need to write it yourself.
• Use FluentValidation.NET which allows you to express your validation rules in a fluent manner. Writing conditional validation rules using this library is not only elegant but very easy. It integrates nicely with ASP.NET MVC and also allows you to easily unit test your validation logic in isolation.

Personally I would go with the FV.NET but you could use any of the other approaches if it better suits your needs.