static List<Countries> openFile(string fileName)
    {
        string line = null;
        List<string> liste = new List<string>();
        List<Countries> countries = new List<Countries>();
        using (StreamReader reader = new StreamReader(fileName)) //fileName = "capitals.txt")
        {
            line = reader.ReadLine();
            while (line != null)
            {
                liste.Add(line);
                line = reader.ReadLine();
            }
        }
        foreach (string ttt in countries)
        {
            string[] test = ttt.Split('t');
            countries.Add(new Countries() { nomPays = test[0], Capitale = test[1] });
        }
        return countries;
    }

//get local folder
StorageFolder local = Windows.Storage.ApplicationData.Current.LocalFolder;
var dataFolder = await local.GetFolderAsync("dataFolder");
var file = await local.OpenStreamForReadAsync("Capitals.txt");

var uri = new System.Uri("ms-appx:///Assets/Capitals.txt");
var file = Windows.Storage.StorageFile.GetFileFromApplicationUriAsync