IndexViewModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace SimpleAuthNancyExample.Models
{
    public class IndexViewModel
    {
        public string ErrorMessage { get; set; }

        public bool HasError
        {
            get { return !string.IsNullOrWhiteSpace(ErrorMessage); }
        }
    }
}