Model Validation / ASP.NET MVC 3 - Conditional Required Attribute

Question

I'm having trouble with my ASP.NET MVC 3 application. I have 2 propertiesin my model whereby I only want 1 of them required in my view based on whichever one is empty. So for example, if I enter a phone number then email is no longer required and vice versa, but if I leave both empty, then either 1 should be required, below is my model:

[Display(Name = "Contact Phone Number:")] [MaxLength(150)] public string ContactPhoneNumber { get; set; }  [Display(Name = "Contact Email Address:")] [MaxLength(100)] public string ContactEmailAddress { get; set; } 

Would I need to create a custom attribute to validate my model and if so, how would I achieve this?

Answer 1

You can implement IValidatableObject on your class and provide a Validate() method that implements your custom logic. Combine this with custom validation logic on the client if you prefer to ensure that one is supplied. I find this easier than implementing an attribute.

public class ContactModel : IValidatableObject {    ...     public IEnumerable<ValidationResult> Validate( ValidationContext context )    {         if (string.IsNullOrWhitespace( ContactPhoneNumber )              && string.IsNullOrWhitespace( ContactEmailAddress ))         {              yield return new ValidationResult( "Contact Phone Number or Email Address must be supplied.", new [] { "ContactPhoneNumber", "ContactEmailAddress" } );         }    } } 

To get everything working at client side you'll need to add the following script to your view:

<script type="text/javascript"> $(function() {     $('form').validate();      $('form').rules('add', {          "ContactPhoneNumber": {              depends: function(el) { return !$('#ContactEmailAddress').val(); }          }      }); }); </script> 

Answer 2

Annotation-based conditional validation can be defined using ExpressiveAnnotations:

[RequiredIf("ContactPhoneNumber == null",     ErrorMessage = "At least email or phone should be provided.")] public string ContactEmailAddress { get; set; }  [RequiredIf("ContactEmailAddress == null",     ErrorMessage = "At least email or phone should be provided.")] public string ContactPhoneNumber { get; set; }