Question

I’m trying to bind two ListBoxes:

<ListBox SelectionChanged="lbApplications_SelectionChanged"
         ItemsSource="{Binding Path=Applications, 
                       UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" />
<ListBox DisplayMemberPath="Message" 
         ItemsSource="{Binding Path=Events, 
                       UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" />

Applications and Events are public properties in Window class.

I set DataContext to this to both list boxes and implement INotifyPropertyChanged in Window class:

 private void NotifyPropertyChanged(string info)
 {
   if (PropertyChanged != null)
     PropertyChanged(this, new PropertyChangedEventArgs(info));
 }

And then after adding new item to Applications or Events I call:

 NotifyPropertyChanged("Events");
 NotifyPropertyChanged("Applications");

The issue is that ListBox is loaded only one time. What am I doing wrong?

Answer 1

Let’s just look at one of the ListBoxes, since they’re both the same, basically.

The code we’re concerned about is this:

<ListBox ItemsSource="{Binding Path=Applications, 
                           UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" />

Since you’re new to WPF, let me say you probably don’t need UpdateSourceTrigger or Mode in there, which leaves us with this:

<ListBox ItemsSource="{Binding Path=Applications}" />

You mentioned that Applications is a public property in your code-behind. You need it to be a DependencyProperty, and you need it to fire events when it changes — most people use an ObservableCollection for this.

So your code-behind will have something like this:

public ObservableCollection<string> Applications
{
    get { return (ObservableCollection<string>)GetValue(ApplicationsProperty); }
    set { SetValue(ApplicationsProperty, value); }
}

public static readonly DependencyProperty ApplicationsProperty =
    DependencyProperty.Register("Applications", 
    typeof(ObservableCollection<string>), typeof(Window1), 
    new UIPropertyMetadata(null));

Then, where you want to add it, you’ll do something like this:

this.Applications = new ObservableCollection<string>();
Applications.Add("Whatever");

Finally, for the “simple” binding syntax to work in the XAML, I usually change the DataContext in my Window (or the root Control element for the file, whatever I’m working in) to

<Window DataContext="{Binding RelativeSource={RelativeSource Self}}" ... >
   ...

Your Applications box will update automatically.