LINQ and Dynamic Predicate Construction at Runtime

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

namespace LINQDynamicSearchDemo {

    public static class Config {
        public static NorthwindDBDataContext GetCurrentContext() {

            NorthwindDBDataContext ctx = HttpContext.Current.Items["RequestContext"] as NorthwindDBDataContext;
            if (ctx != null)
                return ctx;

            // huh? how did that get disposed of?
            throw new NullReferenceException("Somehow the context wasn't created when the request began, or has since been destroyed. Might needs be checking on that.");
        }
    }
}