Custom Validation Attribute with Custom Model Binder in MVC 2

Question

I apologise for the amount of code I have included. I've tried to keep it to a minimum.

I'm trying to have a Custom Validator Attribute on my model as well as a Custom Model binder. The Attribute and the Binder work great seperately but if I have both, then the Validation Attribute no longer works.

Here is my code snipped for readability. If I leave out the code in global.asax the custom validation fires but not if I have the custom binder enabled.

Validation Attribute;

public class IsPhoneNumberAttribute : ValidationAttribute
{
    public override bool IsValid(object value)
    {
        //do some checking on 'value' here
        return true;
    }
}

Useage of the attribute in my model;

    [Required(ErrorMessage = "Please provide a contact number")]
    [IsPhoneNumberAttribute(ErrorMessage = "Not a valid phone number")]
    public string Phone { get; set; }

Custom Model Binder;

public class CustomContactUsBinder : DefaultModelBinder
{
    protected override void OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        ContactFormViewModel contactFormViewModel = bindingContext.Model as ContactFormViewModel;

        if (!String.IsNullOrEmpty(contactFormViewModel.Phone))
            if (contactFormViewModel.Phone.Length > 10)
                bindingContext.ModelState.AddModelError("Phone", "Phone is too long.");
    }
}

Global asax;

System.Web.Mvc.ModelBinders.Binders[typeof(ContactFormViewModel)] = 
  new CustomContactUsBinder();

Technically, you aren't really doing any model binding with your custom model binder. This is just using a model binder for validation only (which isn't what model binders are for). If you really need to have a separate validation for the phone number length, this could be an attribute as well. — Derek Greer
– Derek Greer, Commented Jun 22, 2010 at 22:32
@Derek, whilst I agree with you I am using this as an example to the guys here on what is possible. I have propper binding code in there as well and what I presented here is a snippet only — griegs
– griegs, Commented Jun 22, 2010 at 22:54

Darin Dimitrov · Accepted Answer · 2010-06-18 05:47:26Z

6

Make sure you are calling the base method:

protected override void OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
    ContactFormViewModel contactFormViewModel = bindingContext.Model as ContactFormViewModel;

    if (!String.IsNullOrEmpty(contactFormViewModel.Phone))
        if (contactFormViewModel.Phone.Length > 10)
            bindingContext.ModelState.AddModelError("Phone", "Phone is too long.");

    base.OnModelUpdated(controllerContext, bindingContext);
}

answered Jun 18, 2010 at 5:47

Darin Dimitrov

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1 Comment

griegs Over a year ago

AAAahhhh! Just checked SVN. I removed it this morning for some silly reason and forgot about it! Thanks @Darin.

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