title: Validation type names in unobtrusive client validation rules must be unique
body: <blockquote>
    <p>Validation type names in unobtrusive client validation rules must be
    unique. The following validation type was seen more than once:
    required</p>
  </blockquote>
  
  <p>This is referring to the EmailAddress property, here:</p>
  
  <pre><code>public class LoginModel
  {
      [Required]
      [DataType(DataType.EmailAddress)]
      [Display(Name = "Email")]
      [AdditionalMetadata("Style", "Wide")]
      public string EmailAddress { get; set; }
  
      [Required]
      [DataType(DataType.Password)]
      [Display(Name = "Password")]
      [AdditionalMetadata("Style", "Wide")]
      public string Password { get; set; }
  }
  </code></pre>
  
  <p>I'm not using the same type of validation rule twice here. This works fine locally, but not when deployed to the server. What's the deal?</p>
  
  <p>I did add a reference to <code>DataAnnotationExtensions</code> (<a href="http://dataannotationsextensions.org/">http://dataannotationsextensions.org</a>), could that be causing an issue?</p>
  
  <p><strong>Edit:</strong> removing the reference did not fix the problem. It seems something may be messed up with the IIS configuration?</p>