Question

I am exploring Sharp Architecture and I would like to know how to
access the validation results after calling Entity.IsValid().
I have two scenarios e.g.

1) If the entity.IsValid() return false, I would like to add the
errors to ModelState.AddModelError() collection in my controller.

E.g. in the Northwind sample we have an EmployeesController.Create()
action when we do employee.IsValid(), how can I get access to the
errors?

public ActionResult Create(Employee employee) { 
  if (ViewData.ModelState.IsValid && employee.IsValid()) { 
    employeeRepository.SaveOrUpdate(employee); 
  } 
  // ....
}

[I already know that when an Action method is called, modelbinder
enforces validation rules(nhibernate validator attributes) as it
parses incoming values and tries to assign them to the model object
and if it can’t parse the incoming values  then it register those as
errors in modelstate for each model object property. But what if i
have some custom validation. Thats why we do ModelState.IsValid
first.]

2) In my test methods I would like to test the nhibernate validation
rules as well. I can do entity.IsValid() but that only returns true/
false. I would like to Assert against the actual error not just true/
false.

In my previous projects, I normally use a wrapper Service Layer for
Repositories, and instead of calling Repositories method directly from
controller, controllers call service layer methods which in turn call
repository methods. In my Service Layer all my custom validation rules
resides and Service Layer methods throws a custom exception with a
NameValueCollection of errors which I can easily add to ModelState in
my controller. This way I can also easily implement sophisticated
business rules in my service layer as well. I kow sharp architecture
also provides a Service Layer project. But what I am interested in and
my next question is:

How I can use NHibernate Vaidators to implement sophisticated custom
business rules (not just null,empty, range etc.) and make
Entity.IsValid() to verify those rules too ?

Answer 1

“How I can use NHibernate Vaidators to implement sophisticated custom business rules (not just null,empty, range etc.) and make Entity.IsValid() to verify those rules too ?”

You have to create a custom validation attribute:

here is an example:

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
    public sealed class LoginUniqueAttribute : ValidationAttribute
    {
        private static readonly string DefaultErrorMessage = MUI.LoginNameInUse;

        public LoginUniqueAttribute()
            : base(DefaultErrorMessage)
        {
        }

        public override string FormatErrorMessage(string name)
        {
            return DefaultErrorMessage;
        }

        public override bool IsValid(object value)
        {
            if (string.IsNullOrEmpty((string)value))
            {
                return true;
            }

            var userService = IoC.Resolve<IUserService<User>>();
            return userService.GetByLogins(new[] { (string)value }).Count() == 0;
        }
    }

and usages into a UserInput dto

        [Required]
        [LoginUniqueAttribute]
        [RegularExpression("^[A-Za-z0-9.'\\s]+$", ErrorMessage = "Only characters and digits are allowed")]
        [DisplayNameLocalized(typeof(MUI), "LoginName")]
        public string LoginName { get; set; }

also do not forget to initialize the validation in your global.asax.cs file on Application_Start:

 private void InitializeValidator()
        {
            var provider = new NHibernateSharedEngineProvider();
            NHibernate.Validator.Cfg.Environment.SharedEngineProvider = provider;
        }