A dynamic config object to access <appSettings>

Config.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Configuration;
using System.Dynamic;
using System.Collections.Specialized;

namespace Ox.Models
{
    public class Config : DynamicObject
    {
        private NameValueCollection settings;

        public Config(NameValueCollection s)
        {
            this.settings = s;
        }

        public Config() : this(ConfigurationManager.AppSettings) {}

        public override bool TryGetMember(GetMemberBinder binder, out object result)
        {
            string key = binder.Name.ToLower();
            result = settings[key];
            return result != null;
        } 

    }

}

describe_Config.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using NSpec;
using Ox.Models;
using System.Collections.Specialized;
using Microsoft.CSharp.RuntimeBinder;

namespace Ox.Tests.Models
{
    public class describe_Config : nspec
    {
        void given_app_settings()
        {
            var settings = new NameValueCollection();
            settings.Add("foo", "foo");
            settings.Add("bar", "bar");
            settings.Add("empty", "");
            dynamic config = new Config(settings);

            context["when key exists"] = () =>
            {
                it["then value returned should be non null"] = () =>
                {
                    string value = config.Foo;
                    value.should_not_be_null();
                    value.should_be("foo");
                };

                it["then value returned should be empty string if empty string in app settings"] = () =>
                {
                    string value = config.Empty;
                    value.should_be(string.Empty);
                };

                it["then case sensitivity should not affect returned value"] = () =>
                {
                    string value1 = config.Foo;
                    string value2 = config.foo;
                    value1.should_not_be_null();
                    value2.should_not_be_null();
                    value1.should_be(value2);
                };
            };

            context["when key does not exist"] = () =>
            {
                it["then should throw a RuntimeBinderException"] = expect<RuntimeBinderException>(() => config.FooBar());
            };
        }
    }
}