gistfile1.cs

        [TestMethod]
        public void TestIQueryableExtensions()
        {
            var folks = new List<Person>();

            folks.Add(new Person{ Id = 1, Name = "Patrick" });
            folks.Add(new Person { Id = 2, Name = "James" });

            Assert.AreEqual(folks.GetById(1).Name, "Patrick");
            Assert.AreEqual(folks.GetById(2).Name, "James");
        }
        
        private class Person : IEntityItem
        {
            public int Id { get; set; }
            public string Name { get; set; }
        }