private void SendMails()
        {
            IList <Performance> performances = administrationService.GetPerformancesByDay(CurrentDate);
            IList <Performance> toSend       = new List <Performance>();

            foreach (Performance p in this.GetAllActivePerformancesFromScreen())
            {
                bool shouldAdd = true;
                foreach (Performance p2 in toSend)
                {
                    if (p2.Artist.Id == p.Artist.Id)
                    {
                        shouldAdd = false;
                        break;
                    }
                }
                if (shouldAdd)
                {
                    toSend.Add(p);
                }
            }
            // check old ones removed
            foreach (Performance p in performances)
            {
                bool found = false;
                foreach (Performance p2 in GetAllActivePerformancesFromScreen())
                {
                    if (p.Artist.Id == p2.Artist.Id)
                    {
                        found = true;
                    }
                }
                if (!found)
                {
                    toSend.Add(p);
                }
            }
            administrationService.SendMail(toSend, GetAllActivePerformancesFromScreen());
        }