Using Data Annotations with similar models and the same view to have different validation

Question

I have two separate classes derived from the same interface, but have different validation/data annotations assigned. The requirement is that the same data needs to be collected, but on one screen nothing is required (a save screen), but on the other there are some required fields (a submit/finalize screen.) I've made a PartialView that is to be used in two separate View, one for save, one for final submit.

I've tried using the parent Interface as the View's model, however my validators don't fire (as I expect, I'm guessing that because the Interface itself doesn't have any annotations, nothing will fire.) Is there a way to have the page dynamically choose one class or the other depending on which page I'm using instead of the Interface?

As a side-note, this is being done in ASP.net MVC 3 with Razor.

Apart from the validation requirements, are the two classes the same? do they have the same properties? — Dallas
– Dallas, Commented Nov 18, 2011 at 17:12

counsellorben · Accepted Answer · 2011-11-18 21:31:54Z

You can achieve what you want with one class, and a little lateral thinking.

First, create your class, with the validation baked in. Next, create a custom ModelValidatorProvider inheriting from DataAnnotationsModelValidatorProvider, like so:

public class MyMetadataValidatorProvider : DataAnnotationsModelValidatorProvider
{
    protected override IEnumerable<ModelValidator> GetValidators(ModelMetadata metadata, ControllerContext context, IEnumerable<Attribute> attributes)
    {
        var vals = base.GetValidators(metadata, context, attributes);
        // check to see if any keys have been inserted
        if (context.Controller.ViewData.Keys.Count > 0)
        {
            // check if we have a key named "NoValidate" with a value of true
            // do not return the validtors if we do
            if ((bool)context.Controller.ViewData.FirstOrDefault(k => k.Key == "NoValidate").Value) 
            {
                // we do not want to return our validators, return an empty list
                return new List<ModelValidator>();
            }
        }
        else
        {
            // check if the form has a key named "NoValidate" with a value of true
            // do not return the validtors if we do
            if (context.HttpContext.Request.Form["NoValidate"].ToLowerInvariant() == "true") 
            {
                // we do not want to return our validators, return an empty list
                return new List<ModelValidator>();
            }
        }

        // we want to return our validators
        return vals;
    }
}

Next, register the custom ModelValidatorProvider in Application_Start in Global.asax.cs, like so:

ModelValidatorProviders.Providers.Clear();
ModelValidatorProviders.Providers.Add(new MyMetadataValidatorProvider());

Then, add the following to your view (this will govern whether the validators are returned when the form is POSTed):

@Html.Hidden("NoValidate", ViewData.FirstOrDefault(k => k.Key == "NoValidate").Value)

Finally, add actions like the following:

public ActionResult Index()
{
    var model = new MyModel();
    // this will set validation to appear
    ViewData.Add("NoValidate", false);
    // this will suppress validation 
    ViewData.Add("NoValidate", true);
    return View(model);
}

[HttpPost]
public ActionResult Index(MyModel model)
{
    // we DO want validation, so let's test for it in addition
    // to testing if the ModelState is valid
    if (Request.Form["NoValidate"].ToLowerInvariant() != "true" && ModelState.IsValid)
    {
        ModelState.Clear();
        var newmodel = new MyModel();
        ViewData.Add("NoValidate", true);
        return View(newmodel);
    }

    ViewData.Add("NoValidate", false);
    return View(model);
}

Note that you can control whether the validation appears in your GET action by setting the NoValidate key in ViewData as you want. On the POST, the validation is governed by the form value for NoValidate.

IMPORTANT NOTE: In your action which requires validation, you need to add a test to confirm that the Form does not have the key NoValidate, or its value is not True, in order to enforce that a user cannot avoid the validation.

UPDATE

At first, I had validation only appearing when certain conditions were true. Idecided this was a BAD IDEA, so now validation will only be suppressed if the conditions are true.

This method works very well with the form I'm using due to existing content and functionality of the form. I implemented it into my code and it worked exactly like I wanted. Thanks!

Adam Tuliper · Accepted Answer · 2011-11-18 17:17:07Z

0

Each view should be strongly typed to a separate view model. Each viewmodel then has the validation logic on it (annotations) or inherits from a base that has the required validation on it.

Any logic that cannot be inherited is simply set on your ViewModel itself. If its a small moderl I would consider just copy/paste and two separate viewmodels with their own set of attributes.

You can use AutoMapper to easily map between some concrete object that implements your interface and your ViewModels.

answered Nov 18, 2011 at 17:17

Adam Tuliper

30.2k4 gold badges56 silver badges71 bronze badges

Comments

Dallas · Accepted Answer · 2011-11-18 17:21:04Z

Could you use one class? You can create a filter that allows you to manage the validation errors for an action. In your case you can add an attribute to the Save action and ignore the required errors, but the validations will run for the submit/finalize action. This example will discard all the errors.

public class DontValidateEmailAttribute : ActionFilterAttribute {

  public override void OnActionExecuting(ActionExecutingContext filterContext) {
    var modelState = filterContext.Controller.ViewData.ModelState; 
    var incomingValues = filterContext.Controller.ValueProvider;

    foreach (var key in modelState.Keys) 
      modelState[key].Errors.Clear();

  }
}

I learnt this technique from Steve Sanderson's Pro ASP NET MVC 3. He uses the technique to validate a model that has required fields but the data entry is a multistep wizard. If the value has not been returned in the form post, he removes the errors for that property.

Collectives™ on Stack Overflow

Using Data Annotations with similar models and the same view to have different validation

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related