Listview refreshing on OnAppearing with webservice - wcf

Question

I have some issue updating my online db connected listview page in 2 cases
Adding an item to the list and returning to it with PopAsync
Updating the date with a DatePicker and show data corresponding to
this date
I use a ViewModel to retrieve data from my online db, fill an observablecollection binded to the view. When i open the page with a PushAsync it loads and shows well.
If i do MainPage -> View -> PushAsync to add item page -> PopToRootAsync (main page) -> PushAsync View it shows fine too.
But i need to go on my View right after adding item with PopAsync.
But when i try to have it updated even with OnAppearing it doesn't work. The OnAppearing is triggered but the listview is not updated when i call the ViewModel.
I think the problem is the listview not updated after ClientOnGetSuccesCompleted, when i open the View with a PushAsync the listview is updated while the ObservableCollection is filled.
With OnApprearing it also fill ObservableCollection but no displayed updates.
Tried MessagingCenter but couldn't manage to make it work neither..
Thanks
The ViewModel:
public SuccesViewModel()
{
FillSuccess();
}
public void FillSuccess()
{
SuccesList = new ObservableCollection<Succes>();
var date = App.Date;
BasicHttpBinding binding = CreateBasicHttp();
this.client1 = new BienEtreServiceClient(binding, EndPoint);
this.instance = ((IBienEtreService)client1.InnerChannel);
client1.GetSuccesCompleted += ClientOnGetSuccesCompleted;
client1.GetSuccesAsync(App.UserID, date);
}
private void ClientOnGetSuccesCompleted(object sender, GetSuccesCompletedEventArgs e)
{
SuccesList.Clear();
foreach (Succes item in e.Result)
{
if (item.Date.ToString("yyyy-MM-dd") == App.Date.ToString("yyyy-MM-dd"))
{
SuccesList.Add(item);
}
}
}
XAML:
<ListView x:Name="lv_Succes" ItemsSource="{Binding SuccesList}" HasUnevenRows="True" ItemTapped="Tapped_Succes">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<StackLayout Orientation="Vertical"
Margin="20,8"
Padding="5"
BackgroundColor="#fcf3a8"
MinimumHeightRequest="40"
Opacity="0.7">
<Label x:Name="succes_txt"
Text="{Binding Text}"
FontAttributes="Bold"
TextColor="Black"
FontSize="Medium"/>
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
The code behind the View:
SuccesViewModel SuccesViewModel = new SuccesViewModel();
public Online_Succes()
{
InitializeComponent();
BindingContext = new SuccesViewModel();
}
protected override void OnAppearing()
{
SuccesViewModel.FillSuccess();
base.OnAppearing();
}
The method in OnAppearing is executed, the ObservableCollection filled well, but it doesn't refresh the ListView.

Answer 1

I notice one possible point of failure on your view model: you are creating a new instance to SuccesList on every update call. The binding was made at the first instance you give when setting the binding context of your view, those new instances created on each call of FillSuccess are not binded.
So change your view model to this:
public SuccesViewModel()
{
// Initializing viewModel
SuccesList = new ObservableCollection<Succes>();
BasicHttpBinding binding = CreateBasicHttp();
this.client1 = new BienEtreServiceClient(binding, EndPoint);
this.instance = ((IBienEtreService)client1.InnerChannel);
client1.GetSuccesCompleted += ClientOnGetSuccesCompleted;
// Updating data
FillSuccess();
}
public void FillSuccess()
{
client1.GetSuccesAsync(App.UserID, App.Date);
}
private void ClientOnGetSuccesCompleted(object sender, GetSuccesCompletedEventArgs e)
{
SuccesList.Clear();
foreach (Succes item in e.Result)
if (item.Date.ToString("yyyy-MM-dd") == App.Date.ToString("yyyy-MM-dd"))
SuccesList.Add(item);
}
This should work for you.
I hope it helps.