Question

I’ve an enumerable providing a variable data set of values. The values are generated while runtime from the user.

These values are bound to an ItemsSource of a ListBox

public IEnumerable<string> Items
{
  get { return list; } // list is here a dummy; it does not actually exists
}

listbox.SetBinding(ListBox.ItemsSourceProperty, new Binding { Source = Items });

Now I want to add one fixed item at the beginning. But e.g. lb.Items.Add("abc"); will break runtime. Same for the insert method.

// listbox.Items.Add("abc");
// listbox.Items.Insert(0, "abc");

How do I add a fixed item at the beginning?

Answer 1

You could use Concat if you’re bound to an IEnumerable<string>

listbox.SetBinding(ListBox.ItemsSourceProperty, 
  new Binding { Source = new[] { "abc" }.Concat(Items) }); 

Equally, if it’s a List<string> that you’re binding to – use Insert to add the fixed item at the head after you’ve built it.