LINQ

    public class Customer
    {
        public int CustomerId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int? CustomerTypeId { get; set; }
        public string EmailAddress { get; set; }

    }




public class CustomerRepository
    {
        public Customer Find(List<Customer> customerList, int customerId)
        {
            Customer foundCustomer = null;

            //foreach (var c in customerList)
            //{
            //    if (c.CustomerId == customerId)
            //    {
            //        foundCustomer = c;
            //        break;
            //    }
            //}

            ////Provides an IENumerable to a interaction
            //var query = from c in customerList
            //            where c.CustomerId == customerId
            //            select c;

            //foundCustomer = query.First();

            //FirstOrDefault is a func delagate, A Func delegate defines a function that takes any number of parameters and returns a value of the
            //type specified in the last parameter.
            foundCustomer = customerList.FirstOrDefault(c =>
                                c.CustomerId == customerId);

            //foundCustomer = customerList.FirstOrDefault(c =>
            //                {
            //                    Debug.WriteLine(c.LastName);
            //                    return c.CustomerId == customerId;
            //                });

            //foundCustomer = customerList.Where(c =>
            //                    c.CustomerId == customerId)
            //                    .Skip(1)
            //                    .FirstOrDefault();

            //foundCustomer = customerList.Where(c =>
            //                    c.CustomerId == customerId)
            //                    .Skip(1)
            //                    .FirstOrDefault();

            return foundCustomer;

        }

        public List<Customer> Retrieve()
        {
            List<Customer> custList = new List<Customer>
                    {new Customer()
                          { CustomerId = 1,
                            FirstName="Frodo",
                            LastName = "Baggins",
                            EmailAddress = "fb@hob.me",
                            CustomerTypeId=1},
                    new Customer()
                          { CustomerId = 2,
                            FirstName="Bilbo",
                            LastName = "Baggins",
                            EmailAddress = "bb@hob.me",
                            CustomerTypeId=null},
                    new Customer()
                          { CustomerId = 3,
                            FirstName="Samwise",
                            LastName = "Gamgee",
                            EmailAddress = "sg@hob.me",
                            CustomerTypeId=1},
                    new Customer()
                          { CustomerId = 4,
                            FirstName="Rosie",
                            LastName = "Cotton",
                            EmailAddress = "rc@hob.me",
                            CustomerTypeId=2}};
            return custList;
        }
    }