public static MobileServiceClient MobileService = new
MobileServiceClient("URL");

private IMobileServiceSyncTable<User_Cred> todoGetTable =
App.MobileService.GetSyncTable<User_Cred>();



    private async Task InitLocalStoreAsync()
    {
        if (!App.MobileService.SyncContext.IsInitialized)
        {
            var store = new MobileServiceSQLiteStore("Tale-DB");
            store.DefineTable<User_Cred>();
            await App.MobileService.SyncContext.InitializeAsync(store);
        }
        await SyncAsync();
    }

    private async Task SyncAsync()
    {
        await App.MobileService.SyncContext.PushAsync();
        await todoGetTable.PullAsync("User_Cred",
         todoGetTable.CreateQuery());
    }



    async public void submitAuthBtn_Click(object sender, RoutedEventArgs e)
    {
        await InitLocalStoreAsync();

        GetAuthentication();

    }

    async public void GetAuthentication()
    {
        try
        {

            //IMobileServiceTable<User_Cred> todoTable =
              App.MobileService.GetTable<User_Cred>();

            List<User_Cred> items = await todoGetTable
                .Where(User_Cred => User_Cred.Username ==
                 textBoxUsername.Text)
                .ToListAsync();

            IsAuth = items.Count();



            // Return a List UI control value back to the form

            foreach (var value in items)
            {
                var dialog = new MessageDialog("Welcome Back  " +
                 value.Username);
                await dialog.ShowAsync();
                this.Frame.Navigate(typeof(home));
            }


            if (IsAuth > 0)
            {
                var dialog = new MessageDialog("You are Authenticated");
                await dialog.ShowAsync();


            }
            else
            {
                var dialog = new MessageDialog(" Account Does Not Exist,
                 please Register to get Started.");
                await dialog.ShowAsync();
            }
        }
        catch (Exception em)
        {
            var dialog = new MessageDialog("An Error Occured: " +
             em.Message);
            await dialog.ShowAsync();
        }
    }

    async private void submitAuthBtn_Copy_Click(object sender,
     RoutedEventArgs e)
    {
        try
        {
            User_Cred itemReg = new User_Cred
            {
                Username = textBoxUsername.Text,
                Password = textBoxPassword.Text

            };
            await App.MobileService.GetTable<User_Cred>
             ().InsertAsync(itemReg);
            var dialog = new MessageDialog("Thank you for Registering! Now
            just hit log in");
            await dialog.ShowAsync();

        }
        catch (Exception em)
        {
            var dialog = new MessageDialog("An Error Occured: User Name
           Already exists.");

            await dialog.ShowAsync();
        }
    }

IMobileServiceTable<TodoItem> todoTable =
App.MobileService.GetTable<TodoItem>();
MobileServiceCollection<TodoItem, TodoItem> items;




    public class TodoItem
    {
        public string Id { get; set; }
        public string Title { get; set; }
        public bool Complete { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string ISBN { get; set; }
        public string PublicationDate { get; set; }


    }



    async private void Submit_Click(object sender, RoutedEventArgs e)
    {

        try
        {
            TodoItem item = new TodoItem
            {
                Title = txtBxTitle.Text,
                FirstName = txtBxFName.Text,
                LastName = txtBxLName.Text,
                ISBN = txtBxISBN.Text,
                PublicationDate = txtBxPubDate.Text,
                Complete = false
            };
            await App.MobileService.GetTable<TodoItem>().InsertAsync(item);
            var dialog = new MessageDialog("Successful!");
            await dialog.ShowAsync();
        }
        catch (Exception em)
        {
            var dialog = new MessageDialog("An Error Occured: " +
em.Message);
            await dialog.ShowAsync();
        }
    }

   private async Task RefreshTodoItems()
    {
        MobileServiceInvalidOperationException exception = null;
        try
        {
            // This code refreshes the entries in the list view by querying
            the TodoItems table.
            // The query excludes completed TodoItems
            items = await todoTable
                .Where(TodoItem => TodoItem.Complete == false)
                .ToCollectionAsync();
        }
        catch (MobileServiceInvalidOperationException e)
        {
            exception = e;
        }

        if (exception != null)
        {
            await new MessageDialog(exception.Message, "Error loading
            items").ShowAsync();
        }
        else
        {
            ListItems.ItemsSource = items;
            this.btnRefresh.IsEnabled = true;
        }
    }
private async void CheckBoxComplete_Checked(object sender, RoutedEventArgs
e)
    {
        CheckBox cb = (CheckBox)sender;
        TodoItem item = cb.DataContext as TodoItem;
        await UpdateCheckedTodoItem(item);
    }

    private async Task UpdateCheckedTodoItem(TodoItem item)
    {
   // This code takes a freshly completed TodoItem and updates the
   database. When the MobileService
   // responds, the item is removed from the list

        await todoTable.UpdateAsync(item);
        items.Remove(item);
        ListItems.Focus(Windows.UI.Xaml.FocusState.Unfocused);

        //await SyncAsync(); // offline sync
    }