public StartViewModel()
 {
     images = new PagedEnumerable <byte[]>(
         NBAContext.Instance.Pictures.Select(p => p.Img).ToArray(),
         PAGE_SIZE
         );
     UpdateImageInPage();
     NextImagePage = new ActionCommand(() =>
     {
         images.NextPage();
         UpdateImageInPage();
     });
     PriviusImagePage = new ActionCommand(() =>
     {
         images.PriviusPage();
         UpdateImageInPage();
     });
     OpenLoginPage   = new ActionCommand(() => NavigationManager.OpenPage(new LoginPage()));
     OpenVisitorPage = new ActionCommand(() => NavigationManager.OpenPage(new VisitorMainPage()));
 }