ListBox ignores newly set ItemsSource

Question

I'm currently working on a WPF-Input Window and now I have following problem:

if (e.Key == System.Windows.Input.Key.Enter)
{
     this.variantNumbers.Add(new VariantNumbers {Number = 
     txtVariantNo.Text});
     lstBoxVariants.ItemsSource = this.variantNumbers;
     lstBoxVariants.Visibility = Visibility.Visible;
     txtVariantNo.Text = "";
 }

When I click enter, I want to update the ItemsSource of the ListBox whilst I am setting the ItemsSource new every time I add an element.

What could be wrong here, that my ListBox ignores this setting, the first time I click Enter, it works, the second and following times it doesn't.

Please let me know if someone of you knows what could be wrong here.

Thank You!

It's by design, there is an performance optimization in setter `if(value != _value)` which simply ignores any of your further call. Try to set it to `null` first if you want to *refresh* the value. — Sinatr, Sep 05 '18 at 11:12
Possible duplicate of [WPF ListView: Changing ItemsSource does not change ListView](https://stackoverflow.com/questions/20996288/wpf-listview-changing-itemssource-does-not-change-listview) — Sinatr, Sep 05 '18 at 11:19
While this may work fine, it has a major drawback. The visual representation of all items is re-created each time you reset the ItemsSource. Don't do that. Use an ObservableCollection instead, as shown in the answer. — Clemens, Sep 05 '18 at 19:56

score 1 · Accepted Answer · edited Sep 05 '18 at 19:59

variantNumbers should be an ObservableCollection<VariantNumbers>. In this case you won't have to set ItemsSource each time you add new item.

private readonly ObservableCollection<VariantNumbers> variantNumbers =
    new ObservableCollection<VariantNumbers>();
...

lstBoxVariants.ItemsSource = variantNumbers;
...

if (e.Key == System.Windows.Input.Key.Enter)
{
    variantNumbers.Add(new VariantNumbers { Number = txtVariantNo.Text });
    txtVariantNo.Text = "";     
}

ListBox ignores newly set ItemsSource

1 Answers1