Question

I am trying to make a simple Windows 8/RT app for the store and i have a question about adding items to a ListBox.

In my MainPage i have this code:

public sealed partial class MainPage : Page
{
    public MainPage()
    {
        this.InitializeComponent();
        this.brain = new MainController();
        LoadData();
    }
    public void LoadData()
    {
        brain.GetNotesRepoFile().ReadFile();
        Debug(""+brain.GetNotesRepoFile().GetNotesList().Count);
        for(int i = 0; i < brain.GetNotesRepoFile().GetNotesList().Count; i++)
        {
           notesListBox.Items.Add( // code here );
        }
    }
 }


public class NotesRepositoryFile
{
    // CONSTRUCTOR
    public NotesRepositoryFile()
    {
        this.notesRepository = new List<Note>();
    }
    // Read from file
    public async void ReadFile()
    {
        // settings for the file
        var path = @"Files\Notes.txt";
        var folder = Windows.ApplicationModel.Package.Current.InstalledLocation;

        // acquire file
        var file = await folder.GetFileAsync(path);
        var readThis = await Windows.Storage.FileIO.ReadLinesAsync(file);
        foreach (var line in readThis)
        {
            notesRepository.Add(new Note(line.Split(';')[0], line.Split(';')[1]));
            // check if the item was added
            Debug.WriteLine("Added: " + notesRepository[notesRepository.Count - 1].ToString());
        }
        Debug.WriteLine("File read successfully");
    }

}

My Output is:

0

Added: Test1

Added: Test2

File read successfully

What am i trying to do here is read strings from a file and add them using Items.Add to a listBox. But since the size of the array is 0, even though the items were added successfully that doesnt work.

I dont understand why Debug(“”+brain.GetNotesRepoFile().GetNotesList().Count); is executed before brain.GetNotesRepoFile().ReadFile(); since clearly that is not the case.

Also why does this solution work, and the above doesnt ??

public sealed partial class MainPage : Page
{
    public MainPage()
    {
        this.InitializeComponent();
        this.brain = new MainController();
        ReadFile();
    }
    // Read from file
    public async void ReadFile()
    {
        // settings for the file
        var path = @"Files\Notes.txt";
        var folder = Windows.ApplicationModel.Package.Current.InstalledLocation;

        // acquire file
        var file = await folder.GetFileAsync(path);
        var readThis = await Windows.Storage.FileIO.ReadLinesAsync(file);
        foreach (var line in readThis)
        {
            brain.AddNote(line.Split(';')[0], line.Split(';')[1]);
            notesListBox.Items.Add(brain.GetNotesRepoFile().GetNotesList()[brain.GetNotesRepoFile().GetNotesList().Count - 1].ToString());
        }
        Debug.WriteLine("File read successfully");
    }

}

Answer 1

Well, usage of async and await is wrong is you code, please change according to following codes

First, in NotesRepositoryFile class

public async Task<bool> ReadFile()
{
   //Your code
    if (notesRepository.Count > 0) return true;
            return false;
} 

Second in the MainPage

public async void LoadData()
{
    bool HasNote = await brain.GetNotesRepoFile().ReadFile();

    if (HasNote)
    {
        for (int i = 0; i < brain.GetNotesRepoFile().notesRepository.Count; i++)
        {
                //Your code
        }
    }
 }