Why isnt my listbox getting updated with new items when i add them?

Question

I'm trying to add a new item to the listbox everytime I press the add button but for some reason it only adds the first one, and if I press it again, it doesnt add the second one.

How I am seeing the code right now is that I create a new list named _items and then I add what ever is in my textbox everytime I press the button then I update the ItemSource aswell.

How do I make it add a new item everytime I press the AddBtn?

List<string> _items = new List<string>();


private void addBtn_Click(object sender, RoutedEventArgs e)
{
    _items.Add(recipentTextbox.Text);
    recipientLb.ItemsSource = _items;
}

Am I correct in guessing that this is WPF and you tagged it `winforms` just for the sake of misdirection? — 15ee8f99-57ff-4f92-890c-b56153, Jan 09 '17 at 19:15

score 2 · Answer 1 · edited Jan 09 '17 at 19:32

2

Try using an ObservableCollection<string> instead of List<string>. The ObservableCollection supports data binding, and will update the target property.

edited Jan 09 '17 at 19:32

Clemens

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answered Jan 09 '17 at 19:15

Peter

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I used ```BindingList``` what's the difference? – John V Dole Jan 09 '17 at 19:17
[http://stackoverflow.com/questions/4284663/difference-between-observablecollection-and-bindinglist] – Peter Jan 09 '17 at 19:18
Yeah you need the ObservableCollection. Make sure you initialize it in the constructor and then only clear it never replace it as then the binding will break. – Kelly Jan 10 '17 at 02:57

score 0 · Answer 2 · answered Jan 09 '17 at 19:17

0

ObservableCollection<string> _items = new ObservableCollection<string>();

//  Or whatever your constructor is
public MainWindow()
{
    recipientLb.ItemsSource = _items;
}

private void addBtn_Click(object sender, RoutedEventArgs e)
{
    _items.Add(recipentTextbox.Text);
}

answered Jan 09 '17 at 19:17

15ee8f99-57ff-4f92-890c-b56153

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What's the difference betweek ```BindingList``` and ```ObservableCollection``` ? – John V Dole Jan 09 '17 at 19:18
@JonnyKhanas ObservableCollection supersedes BindingList. IIRC BindingList is a winforms thing or something; don't use it with WPF – 15ee8f99-57ff-4f92-890c-b56153 Jan 09 '17 at 19:19
@JonnyKhanas WPF controls expect collections to implement `INotifyCollectionChanged`, which `ObservableCollection` does and `BindingList` does not. – 15ee8f99-57ff-4f92-890c-b56153 Jan 09 '17 at 19:21

Why isnt my listbox getting updated with new items when i add them?

2 Answers2