public EFServersDataProvider(DataContextProvider db) : base(db)
 {
 }
        //private readonly MailSenderDB _db;
        //private readonly ICollection<Recipient> _items; //DBSet
        //public EFRecipientsDataProvider(MailSenderDB db) { _db = db; _items = GetAll().ToList(); }


        //public EFRecipientsDataProvider(MailSenderDB db) : base(db) { }
        public EFRecipientsDataProvider(DataContextProvider db) : base(db)
        {
        }
 public EFEmailsDataProvider(DataContextProvider db) : base(db)
 {
 }
 public EFSchedularTasksDataProvider(DataContextProvider db) : base(db)
 {
 }
 protected EFDataProvider(DataContextProvider db)
 {
     _db = db;
 }