using System;
    using System.Collections.Generic;

namespace EmailSenderProgram
{
    internal class Program
    {
        /// <summary>
        /// This application is run everyday
        /// </summary>
        /// <param name="args"></param>
        private static void Main(string[] args)
        {
            Console.WriteLine("Send Welcomemail");
            bool success = DoEmailWork();

#if DEBUG

            Console.WriteLine("Send Comebackmail");
            success = DoEmailWork2("CompanyComebackToUs");
#else

            if (DateTime.Now.DayOfWeek.Equals(DayOfWeek.Monday))
            {
                Console.WriteLine("Send Comebackmail");
                success = DoEmailWork2("CompanyComeBackToUs");
            }
#endif

if (success == true)
                {
                    Console.WriteLine("All mails are sent, I hope...");
                }

if (success == false)
                {
                    Console.WriteLine("Oops, something went wrong when sending mail (I think...)");
                }
                Console.ReadKey();
            }

            /// <summary>
            /// Send Welcome mail
            /// </summary>
            /// <returns></returns>
            public static bool DoEmailWork()
            {
                try
                {

List<Customer> e = DataLayer.ListCustomers();


for (int i = 0; i < e.Count; i++)
                    {

if (e[i].CreatedDateTime > DateTime.Now.AddDays(-1))
                        {


System.Net.Mail.MailMessage m = new System.Net.Mail.MailMessage();

                            m.To.Add(e[i].Email);
Add subject
                            m.Subject = "Welcome as a new customer at Company!";
Send mail from company@info.com
                            m.From = new System.Net.Mail.MailAddress("compay@info.com);

m.Body = "Hi " + e[i].Email +
                                     "<br>We would like to welcome you as customer on our site!<br><br>Best Regards,<br>Company Team";
    #if DEBUG

Console.WriteLine("Send mail to:" + e[i].Email);
    #else
Create a SmtpClient to our smtphost: yoursmtphost
                        System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient("yoursmtphost");
                    smtp.Send(m);
#endif
                    }
                }
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

        /// <summary>
        /// Send Customer ComebackMail
        /// </summary>
        /// <param name="v"></param>
        /// <returns></returns>
        private static bool DoEmailWork2(string v)
        {
            try
            {
                //List all customers
                List<Customer> e = DataLayer.ListCustomers();
                //List all orders
                List<Order> f = DataLayer.ListOrders();

                //loop through list of customers
                foreach (Customer c in e)
                {
                    // We send mail if customer hasn't put an order
                    bool Send = true;
                    //loop through list of orders to see if customer don't exist in that list
                    foreach (Order o in f)
                    {
                        // Email exists in order list
                        if (c.Email == o.CustomerEmail)
                        {
                            //We don't send email to that customer
                            Send = false;
                        }
                    }

                    //Send if customer hasn't put order
                    if (Send == true)
                    {
                        //Create a new MailMessage
                        System.Net.Mail.MailMessage m = new System.Net.Mail.MailMessage();
                        //Add customer to reciever list
                        m.To.Add(c.Email);
                        //Add subject
                        m.Subject = "We miss you as a customer";
                        m.From = new System.Net.Mail.MailAddress("company@info.com");
                        //Add body to mail
                        m.Body = "Hi " + c.Email +
                                 "<br>We miss you as a customer. Our shop is filled with nice products. Here is a voucher that gives you 50 kr to shop for." +
                                 "<br>Voucher: " + v +
                                 "<br><br>Best Regards,<br>Company Team";
#if DEBUG
                        //Don't send mails in debug mode, just write the emails in console
                        Console.WriteLine("Send mail to:" + c.Email);
#else
Create a SmtpClient to our smtphost: yoursmtphost
                        System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient("yoursmtphost");

                        smtp.Send(m);
    #endif
                        }
                    }
                    return true;
                }
                catch (Exception)
                {
                    return false;
                }
            }
        }
}

namespace EmailSenderProgram
{
    public class Customer
    {
        public string Email { get; set; }
        public DateTime CreatedDateTime { get; set; }
    }

    public class Order
    {
        public string CustomerEmail { get; set; }
        public DateTime OrderDatetime { get; set; }
    }

    class DataLayer
    {
        /// <summary>
        /// Mockup method for all customers
        /// </summary>
        public static List<Customer> ListCustomers()
        {
            return new List<Customer>()
                       {
                           new Customer(){Email = "mail1@mail.com", CreatedDateTime = DateTime.Now.AddHours(-7)},
                           new Customer(){Email = "mail2@mail.com", CreatedDateTime = DateTime.Now.AddDays(-1)},
                           new Customer(){Email = "mail3@mail.com", CreatedDateTime = DateTime.Now.AddMonths(-6)},
                           new Customer(){Email = "mail4@mail.com", CreatedDateTime = DateTime.Now.AddMonths(-1)},
                           new Customer(){Email = "mail5@mail.com", CreatedDateTime = DateTime.Now.AddMonths(-2)},
                           new Customer(){Email = "mail6@mail.com", CreatedDateTime = DateTime.Now.AddDays(-5)}
                       };
        }

        /// <summary>
        /// Mockup method for listing all orders
        /// </summary>
        public static List<Order> ListOrders()
        {
            return new List<Order>()
                       {
                           new Order(){CustomerEmail = "mail3@mail.com", OrderDatetime = DateTime.Now.AddMonths(-6)},
                           new Order(){CustomerEmail = "mail5@mail.com", OrderDatetime = DateTime.Now.AddMonths(-2)},
                           new Order(){CustomerEmail = "mail6@mail.com", OrderDatetime = DateTime.Now.AddDays(-2)}
                       };
        }
    }
}