Validating ModelState in WebApi

gistfile1.cs

    public class ValidateModelStateAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            if (!actionContext.ModelState.IsValid)
            {
                var errors = from k in actionContext.ModelState.Keys
                             from e in actionContext.ModelState[k].Errors
                             select new ValidationError { ParameterName = k, ErrorMessage = e.ErrorMessage };

                var response = actionContext.Request.CreateResponse<ValidationError[]>(HttpStatusCode.BadRequest, errors.ToArray());
                throw new HttpResponseException(response);
            }
            
            base.OnActionExecuting(actionContext);
        }
    }

    public class ValidationError
    {
        public string ParameterName { get; set; }
        public string ErrorMessage { get; set; }
    }