There is a form. Here is its contents

<Grid> <Grid.ColumnDefinitions> <ColumnDefinition/> <ColumnDefinition/> </Grid.ColumnDefinitions> <ListBox ItemsSource="{Binding Col1}" DisplayMemberPath="Name" SelectedValuePath="Sum" SelectedItem="{Binding Selected, Mode=TwoWay}"/> <ListBox Grid.Column="1" ItemsSource="{Binding Col2}" DisplayMemberPath="Name" SelectedValuePath="Sum" SelectedItem="{Binding Selected, Mode=TwoWay}" MouseDoubleClick="ListBox_MouseDoubleClick"/> </Grid>

Here is its background (it’s also a view)

 public partial class MainWindow : Window, INotifyPropertyChanged { Output _selected; public event PropertyChangedEventHandler PropertyChanged; public ObservableCollection<Output> Col1 { get; set; } public ObservableCollection<Output> Col2 { get; set; } public Output Selected { get { return _selected; } set { _selected = value; OnPropertyChanged(nameof(Selected)); } } public MainWindow() { Col1 = new ObservableCollection<Output> { new Output {Name="name_1", Sum=1 }, new Output {Name="name_2", Sum=2 }, new Output {Name="name_3", Sum=3 }, new Output {Name="name_4", Sum=4 } }; Col2 = new ObservableCollection<Output> { Col1[2], Col1[3], new Output {Name="name_5", Sum=5 }, new Output {Name="name_6", Sum=6 } }; DataContext = this; InitializeComponent(); } private void ListBox_MouseDoubleClick(object sender, MouseButtonEventArgs e) { Selected = null; } void OnPropertyChanged(string name) { PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name)); } }

I start, I select the first item in the left sheet. Everything's Alright. I select the last item in the left sheet (name 4). The corresponding item is highlighted in the second sheet. Now I select the last item in the second sheet ...

It was expected that in this case the selection will be removed in the left sheet, because this item is not in the linked collection. But the selection remains. Why?

UPD:

But the saddest thing turned out to be not even this, but the fact that when you move a tab on the sheets (or with a mouse, clicking on already selected visually items), the Selected property does not change. This will be seen if you attach a window title to it.

 Title="{Binding Selected.Name}"
  • And what makes you think that this should work at all? - Monk
  • This is a well-known story: ListBox and its “colleagues” do not behave very intuitively if the SelectedItem is attached to an item that is not in the list. - VladD
  • What you write in the UPD is correct, and it should be so. There is a difference between Selected and Focused. The tab switches the focus, the selection does not automatically follow the focus. Worse, the selected elements can be many, and the focus is one. - VladD
  • one
    I would just use two properties in the view-view, when changing one of them I cleaned the other. In my opinion will behave as you want. - Monk

1 answer 1

It seems as if there are problems with binding, it is simply ignored, i.e. in this case, there will be no change in the select box if you try to specify an element that does not exist in ItemsSource. If the behavior of the list boxes given by the author of the question is really necessary, then you need to make 2 Selected fields, i.e. each listbox has its own, and a bit of logic in set blocks. for example, reinstalling or resetting the neighboring Select, if necessary (well, to win the looping of the installation of these fields from each other)

About the "most sad" - I think this is simply a consequence of the broken binding.