CODEWITHSUNDEEP
wpf
Pier Giordano
Pier Giordano

Reputation: 3

WPF Xaml updating listView to List<string> using INotifyPropertyChanged

I have a simple problem. I have a listView and it's datasource is a List. It is not updated immediately, but only when the codeflow ends. What's the problem?

Below xaml:

<ListView x:Name="listView" ItemsSource="{Binding InfoBancaDatiAttuale}" HorizontalAlignment="Left" Height="130" Margin="212,34,0,0" VerticalAlignment="Top" Width="310">
        <ListView.View>
            <GridView>
                <GridViewColumn/>
            </GridView>
        </ListView.View>
    </ListView>

Below xaml.cs:

    private List<string> _infoBancaDatiAttuale;
    public List<string> InfoBancaDatiAttuale
    {
        get { return _infoBancaDatiAttuale; }
        set
        {
            _infoBancaDatiAttuale = value;
            onPropertyChanged("InfoBancaDatiAttuale");
        }
    }
    private void AddToListAndNotify(List<string> list, string value, string propertyNotify)
    {
        List<string> tempList = list;
        tempList.Add(value);
        InfoBancaDatiAttuale = tempList;
    }

In xaml.cs file I have also a procedure that perform instruction and should refresh UI. Percentage refresh a ProgressBar and I see that is update instantanely but InfoBancaDatiAttuale not refresh until the method finish.

public void performInstruction() {
    Percentage = (int)((1 * 100) / 11);
    AddToListAndNotify(InfoBancaDatiAttuale, "1) Eseguo login", "InfoBancaDatiAttuale");
    //...instruction
    Percentage = (int)((2 * 100) / 11);
    AddToListAndNotify(InfoBancaDatiAttuale, "2) Another operation", "InfoBancaDatiAttuale");
    //...instruction
    Percentage = (int)((3 * 100) / 11);
    AddToListAndNotify(InfoBancaDatiAttuale, "3) Another operation", "InfoBancaDatiAttuale");
}

What's the problem?

Upvotes: 0

Views: 39

Answers (2)

Dean Chalk
Dean Chalk

Reputation: 20461

Your issue is nothing to do with INotifyPropertyChanged, INotifyCollectionChanged and you dont need to use an ObservableCollection (although it would be slightly more efficient)

Your problem is that your performInstruction Method is running on the UI Thread and the Dispatcher is unable to update the user interface until the method has completed, which is why nothing happens until the method has completed.

What you could to is:

    public void performInstruction() {
        Task.Run(() => {
           Percentage = (int)((1 * 100) / 11);
           AddToListAndNotify(InfoBancaDatiAttuale, "1) Eseguo login", 
   "InfoBancaDatiAttuale");
           //...instruction
           Percentage = (int)((2 * 100) / 11);
           AddToListAndNotify(InfoBancaDatiAttuale, "2) Another operation", 
   "InfoBancaDatiAttuale");
           //...instruction
           Percentage = (int)((3 * 100) / 11);
           AddToListAndNotify(InfoBancaDatiAttuale, "3) Another operation", 
   "InfoBancaDatiAttuale");
       };
    }

And before anyone suggests that you need to marshal the property changes up to the dispatcher thread, I can assure you that it isnt necessary.

Upvotes: 1

fhnaseer
fhnaseer

Reputation: 7277

You should use ObservableCollection<string>. It will fire the CollectionChanged event of the INotifyCollectionChanged interface whenever an item is added to or removed from the collection.

private ObservableCollection<string> _items;
public ObservableCollection<string> Items => _items ?? (_items = new ObservableCollection<string>());

Upvotes: 0

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