Source code for this blog post: http://blog.robseder.com/2015/01/29/generics-lambda-expressions-and-linq/

Customer.cs

    public class Customer
    {
        public Guid CustomerId { get; set; }
        public String FirstName { get; set; }
        public String LastName { get; set; }

        public override string ToString()
        {
            return String.Format("{0} {1}", FirstName, LastName);
        }
    }

Program.cs

    internal class Program
    {
        private static void Main(string[] args)
        {
            IEnumerable<Customer> customersRaw = GetAllCustomers();
            Debug.WriteLine("Raw, unsorted:");
            foreach (Customer customer in customersRaw)
            {
                Debug.WriteLine(customer);
            }

            Debug.WriteLine("-----------------------------------");

            IEnumerable<Customer> customersFiltered =
                GetByFilter(item => item.LastName.Contains("i"));

            Debug.WriteLine("Customers with 'i' in their last name:");
            foreach (Customer customer in customersFiltered)
            {
                Debug.WriteLine(customer);
            }

            Debug.WriteLine("-----------------------------------");

            IEnumerable<Customer> customersOrdered =
                GetAndSort(item => item.FirstName);

            Debug.WriteLine("Customers sorted by first name:");
            foreach (Customer customer in customersOrdered)
            {
                Debug.WriteLine(customer);
            }

            Debugger.Break();
        }

        private static IEnumerable<Customer> GetAllCustomers()
        {
            List<Customer> customers = new List<Customer>
            {
                new Customer() {CustomerId = Guid.NewGuid(), FirstName = "Adam", LastName = "Zelda"},
                new Customer() {CustomerId = Guid.NewGuid(), FirstName = "Carlie", LastName = "Xavier"},
                new Customer() {CustomerId = Guid.NewGuid(), FirstName = "Brianna", LastName = "Yankovic"}
            };

            return customers;
        }

        private static IEnumerable<Customer> GetByFilter(Func<Customer, Boolean> whereClause)
        {
            if (whereClause == null)
                throw new ArgumentNullException("whereClause");

            IEnumerable<Customer> customers = GetAllCustomers();

            return customers.Where(whereClause);
        }

        private static IEnumerable<Customer> GetAndSort<TKey>(Func<Customer, TKey> orderBy)
        {
            if (orderBy == null)
                throw new ArgumentNullException("orderBy");

            IEnumerable<Customer> customers = GetAllCustomers();

            return customers.OrderBy(orderBy);
        }
    }