Question

i have a dictonary

public class TAGs :INotifyPropertyChanged{
private Dictionary<string, string[]> _items = new Dictionary<string,string[]>();
 ...............
public string[] Keys
    {
        get { return Items.Keys.ToArray(); }
    }

}

i want to create 2 list, 1 list for the key and the other list contain the values of the selected keys, i tried this but it doesnt work

<ListBox x:Name="TagNameList" ItemsSource="{Binding Keys}"/>
<ListBox ItemsSource="{Binding Items[{Binding SelectedItem,ElementName=TagNameList}]}"/>

i contained them to a grid and their datacontext is an object of TAGs, the 1st listbox is working fine as its simple binding to a property but the 2nd list, isnt working
any help?

Answer 1

"{Binding Items[{Binding SelectedItem,ElementName=TagNameList}]}" isn’t valid xaml. You can’t do a binding inside a path since the path is constructed at compile time.

When encountering this myself I’ve simply ended up binding something else to the SelectedItem of one ListBox and then when that gets notified of a change, also fire a NotifyPropertyChanged on another property exposing Items[selectedKey] to which my second ListBox is bound.

xaml:

<ListBox x:Name="TagNameList" ItemsSource="{Binding Keys}" SelectedItem={Binding Selected}/>
<ListBox ItemsSource="{Binding ValueFromKey}"/>

C#:

string _selected;
public string Selected
{
    get { return _selected; }
    set 
    { 
        _selected= value; 
        OnPropertyChanged("Selected");
        OnPropertyChanged("ValueFromKey");
    }
}

public string[] ValueFromKey
{
    get { return Items[Selected]; }
}