title: Validating enums with FluentValidation
body: <p>I'm using FluentValidation.WebApi 6.2.1.0 in Web API project. Is there a way to validate enum with FluentValidation and return custom message?</p>
  
  <p>my controller action is as following,</p>
  
  <pre><code>public IHttpActionResult Get([FromUri]CheckUpdateVM info)
  {
      ...
  }
  </code></pre>
  
  <p>My Model,</p>
  
  <pre><code>[Validator(typeof(CheckUpdateVMValidator))]
  public class CheckUpdateVM
  {
      public DeviceTypes Device { get; set; }
  }
  </code></pre>
  
  <p>I'm looing for something like this,</p>
  
  <pre><code>public class CheckUpdateVMValidator : AbstractValidator&lt;CheckUpdateVM&gt;
  {
      public CheckUpdateVMValidator()
      {
          RuleFor(x =&gt; x.Device).Must(x =&gt; Enum.IsDefined(typeof(DeviceTypes), x)).WithMessage("xxx");
      }
  }
  </code></pre>
  
  <p>With above code, Model binder validate the value of "Device" parameter and response with an error. but I can't customize the error message. (If I set the "Device" property type to string, this works fine.)</p>