/// <summary>
 /// Creates a Singleton instance of the DAL.
 /// </summary>
 /// <returns>the data access layer.</returns>
 public static DataAccessLayer CreateInstance()
 {
     if (Instance==null)
     {
         Instance = new DataAccessLayer();
     }
     return Instance;
 }
        public MainWindow()
        {
            InitializeComponent();

            _dataAccessLayer = DataAccessLayer.CreateInstance();
        }