How to update ItemsSource automatically from own collection?

Question

I have created my own collection and implemented INotifyCollectionChanged.

public class ObservableSortedSet<T> : SortedSet<T>, INotifyCollectionChanged
{
    public event NotifyCollectionChangedEventHandler CollectionChanged;

    public new bool Add(T item)
    {
        var result = base.Add(item);
        if (result)
            CollectionChanged?.Invoke(item,
                new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item));
        return result;
    }

    public new bool Remove(T item)
    {
        var result = base.Remove(item);
        if (result)
            CollectionChanged?.Invoke(item,
                new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, item));
        return result;
    }

    public new void Clear()
    {
        base.Clear();
        CollectionChanged?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
    }
}

However when I try to use this collection as ItemsSource in views, they do not update automatically when I e.g. remove an item. As I seen in other questions here, I should implement INotifyCollectionChanged. I did this and yet it doesn't work. Any suggestions?

wake-0 · Accepted Answer · 2016-06-05T19:14:57.573

2

The reason why your remove method does not work is that you have to add the index of the removed element.

I tried it this way and it does work:

View codebehind:

public ObservableSortedSet<String> Values { get; private set; }

    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;

        Values = new ObservableSortedSet<string>();
        Values.Add("Test0");
        Values.Add("Test1");
        Values.Add("Test2");
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        Values.Add("Test" + Values.Count);
    }
}

View:

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="*" />
        <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>

    <ListView ItemsSource="{Binding Path=Values}">
        <ListView.ItemTemplate>
            <DataTemplate>
                <Label Content="{Binding}" />
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

    <Button Grid.Row="1" Content="Add" Click="Button_Click"/>
</Grid>

edited Jun 05 '16 at 19:14

answered Jun 05 '16 at 18:52

wake-0

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Did you try to remove an item? – Dominik Murzynowski Jun 05 '16 at 19:15
yes and the remove works, when the index of the removed element is added. – wake-0 Jun 05 '16 at 19:16
I assume I should add this to invocation of CollectionChanged. How can I get an index of removed item, or can I use just 0? – Dominik Murzynowski Jun 05 '16 at 19:22
Thats the problem :D – wake-0 Jun 05 '16 at 19:26
has you already read this [link](http://stackoverflow.com/questions/5883870/inotifycollectionchanged-help) – wake-0 Jun 05 '16 at 19:33
Maybe there is a problem with synchronization because i tried this code `public new bool Remove(T item) { bool result = false; for (int i = 0; i < Count; i++) { if (this.ElementAt(i).Equals(item)) { result = base.Remove(item); CollectionChanged?.Invoke(item, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, item, i)); break; } } return result; }` – wake-0 Jun 05 '16 at 19:41
Should the debugger indicate that I have some listener to my event? – Dominik Murzynowski Jun 05 '16 at 19:47
1

Still not working, nevermind, I will refresh my ItemsSources manually. Thanks for help. – Dominik Murzynowski Jun 05 '16 at 19:52

How to update ItemsSource automatically from own collection?

1 Answers1