UI Doesnt change after observable collection change

Question

Hi i have observablecollection and i takes data from server and when it finish i want refresh list on my page.Data is coming but i cant see it on screen i cant find my error. I implement INotifypropertychanged bu i think its not working well. When i put breakpoint i see PropertyChanged event every time is null.

My class

public class Ulke:INotifyPropertyChanged
{
    private int _ulkeID;
    public int UlkeID 
    { 
        get { return _ulkeID; } 
        set { _ulkeID = value; NotifyPropertyChanged(); } 
    }

    private string _adi;
    public string Adi 
    { 
        get { return _adi; } 
        set { _adi = value; NotifyPropertyChanged(); } 
    }

    public string DiyanetID { get; set; }
    public bool EyaletVarmi { get; set; }

    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

UlkeRepository Class

public class UlkeRepository : INotifyPropertyChanged
{
    public UlkeRepository()
    {
        _ulkeler = new ObservableCollection<Ulke>();
        ulkeler.Add(new Ulke { UlkeID = 3, EyaletVarmi = true, DiyanetID = "3", Adi = "Moliba" });
        ulkeler.Add(new Ulke { UlkeID = 5, EyaletVarmi = true, DiyanetID = "3", Adi = "As" });
    }

    private ObservableCollection<Ulke> _ulkeler;
    public ObservableCollection<Ulke> ulkeler 
    { 
            get { return _ulkeler; }
            set { _ulkeler = value; NotifyPropertyChanged(); } 
    }

    public async Task UlkeGetir()
    {
        JsonDownloader js = new JsonDownloader();
        var result = await js.GetDataFromUrl<Ulke>("http://www.example.com/A/UlkeGetir");
        ulkeler = result;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

}

MyPageLoaded code

   this.DataContext = ulke.ulkeler;
   liste.DataContext = ulke.ulkeler;         
   ulke.UlkeGetir();

Xaml Code

<ListBox x:Name="liste"
         ItemsSource="{Binding Mode=TwoWay}" SelectionChanged="liste_SelectionChanged">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Adi}"/>
                </DataTemplate>
            </ListBox.ItemTemplate>
 </ListBox>

Answer 1

Updated Solution after taking a look at the source:

Everything is working, you just need to pay attention to the compiler warnings.

HubPage.xaml.cs

Function UlkeYukle Update (you forgot to await)

UlkeRepository ulke;
private async void UlkeYukle()
{
    ulke = new UlkeRepository();        
    await ulke.UlkeGetir();         // you forgot this       
}


// this is a function to test your OnPropertyChange
private void Button_Click(object sender, RoutedEventArgs e)
{
    ulke.ulkeler.Insert(0, new Ulke { UlkeID = 5, EyaletVarmi = true, DiyanetID = "3", Adi = "A_TEST" }); // inssert at top
    ulke.ulkeler[0].Adi = "Changing Title Again";
}

For debug purpose I added a Button to the template (so we can test if it updates after the fact)

HubPage.xaml

<HubSection x:Uid="HubSection1" x:Name="hub1" Header="SECTION 1" DataContext="{Binding Mode=TwoWay}" HeaderTemplate="{ThemeResource HubSectionHeaderTemplate}">
    <DataTemplate>
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="80*"/>
                <RowDefinition Height="20*"/>
            </Grid.RowDefinitions>
            <ListView 
            ItemsSource="{Binding Mode=TwoWay}"
            IsItemClickEnabled="True"
            ItemClick="GroupSection_ItemClick"
            ContinuumNavigationTransitionInfo.ExitElementContainer="True">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Margin="0,0,0,27.5">
                            <TextBlock Text="{Binding Adi}" Style="{ThemeResource ListViewItemTextBlockStyle}" />
                        </StackPanel>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
            <Button Click="Button_Click" Grid.Row="1"></Button>
        </Grid>
    </DataTemplate>
</HubSection>

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