MVC strongly-typed view, and server side setting properties before sending to lower layers?

Question

I have a layered application that send commands to the business layer (actually, the application is based on ncqrs framework, but I don't think it's important here).

A command looks like this :

public class RegisterUserCommand : CommandBase
{
    public string UserName { get; set; }
    public string Email{ get; set; }
    public DateTime RegistrationDate { get; set; }
    public string ApiKey {get; set;} // edit
}

There is no logic in this class, only data.

I want to have the users type their user name, email and I want the system to use the current date to build the command.

What is best between :

1. create a strongly typed view based on the RegisterUserCommand, then inject the date and the APi Key just before sending it to the business layer ?

2. create a RegisterUserViewModel class, create the view with this class and create the command object based on the view input ?

I wrote the following code (for the solution n°2) :

public class RegisterController : Controller
{
    //
    // GET: /Register/

    public ActionResult Index()
    {
        return View();
    }

    [HttpPost]
    public ActionResult Index(RegisterUserViewModel registrationData)
    {

        var service = NcqrsEnvironment.Get<ICommandService>();
        service.Execute(
            new RegisterUserCommand
            {
                RegistrationDate = DateTime.UtcNow,
                Email= registrationData.Email,
                UserName= registrationData.Name,
                ApiKey = "KeyFromConfigSpecificToCaller" // edit
            }
            );

        return View();
    }


    public class RegisterUserViewModel
    {
        [Required]
        [StringLength(16)]
        public string Name { get; set; }
        [Required]
        [StringLength(64)]
        public string Email{ get; set; }
    }
}

This code is working... but I wonder if I choose the correct way...

thanks for advises

[Edit] As the Datetime seems to cause misunderstanding, I added another property "ApiKey", that should also be set server side, from the web layer (not from the command layer)

[Edit 2] try the Erik suggestion and implement the 1st solution I imagined :

[HttpPost]
public ActionResult Index(RegisterUserCommand registrationCommand)
{

    var service = NcqrsEnvironment.Get<ICommandService>();
    registrationCommand.RegistrationDate = DateTime.UtcNow;
    registrationCommand.ApiKey = "KeyFromConfigSpecificToCaller";
    service.Execute(
        registrationCommand
        );

    return View();
}

... Is it acceptable ?

Answer 1

I think you would be better off with option #2, where you would have a separate ViewModel and a Command. While it may seem redundant (to an extent), your commands are really messages from your web server to your command handler. Those messages may not be formatted the same as your ViewModel, nor should they be. And if you're using NCQRS as is, you would then have to map your commands to your AR methods and constructors.

While it may save you a little bit of time, I think you pigeon-hole yourself in to modeling your domain after your ViewModels, and that should not be the case. Your ViewModels should be a reflection of what your user experiences and sees; your domain should be a reflection of your business rules and knowledge, and are not always reflected in your view.

It may seem like a bit more work now, but do yourself a favor and keep your commands separate from your view models. You'll thank yourself later.

I hope this helps. Good luck!

Answer 2

I would recommend putting this into the constructor of the RegisterUserCommand class. That way the default behavior is always to set it to DateTime.UtcNow, and if you need to set it to something explicitly you can just add it to the object initializer. This will also help in scenarios where you're using this class in other parts of your project, and you forget to set the RegistrationDate explicitly.

public class RegisterUserCommand : CommandBase
{
    public string UserName { get; set; }
    public string Email{ get; set; }
    public DateTime RegistrationDate { get; set; }

    public RegisterUserCommand()
    {
        RegistrationDate = DateTime.UtcNow;
    }
}

And the Controller

public class RegisterController : Controller
{
    //
    // GET: /Register/

    public ActionResult Index()
    {
        return View();
    }

    [HttpPost]
    public ActionResult Index(RegisterUserViewModel registrationData)
    {

        var service = NcqrsEnvironment.Get<ICommandService>();
        service.Execute(
            new RegisterUserCommand
            {
                Email= registrationData.Email,
                OpenIdIdentifier = registrationData.OpenIdIdentifier
            }
            );

        return View();
    }


    public class RegisterUserViewModel
    {
        [Required]
        [StringLength(16)]
        public string Name { get; set; }
        [Required]
        [StringLength(64)]
        public string Email{ get; set; }
    }
}

Answer 3

I would use number 1 and use the system.componentmodel.dataannotations.metadatatype for validation.

I created an example (answer) for another SO question Here.

This allows you to keep your model in another library, validate the fields and show the fields like you would internal/private classes with DataAnnotations. I'm not a big fan of creating a completely separate class for a view that has no additional value while having to ORM the data back to another class. (If you had additional values like dropdown list values, or default values then I think it would make sense).

Instead of

[HttpPost]
public ActionResult Index(RegisterUserViewModel registrationData)
{

    var service = NcqrsEnvironment.Get<ICommandService>();
    service.Execute(
        new RegisterUserCommand
        {
            RegistrationDate = DateTime.UtcNow,
            Email= registrationData.Email,
            UserName= registrationData.Name,
            ApiKey = "KeyFromConfigSpecificToCaller" // edit
        }
        );

    return View();
}

You can have

[HttpPost]
public ActionResult Index(RegisterUserCommand registrationData)
{

    var service = NcqrsEnvironment.Get<ICommandService>();

    registrationData.ApiKey = "KeyFromConfigSpecificToCaller";

    service.Execute(registrationData);

    return View();
}