WP7 Database and Casting error

Question

i am a newbie for develop in c# i am studing this example http://msdn.microsoft.com/en-us/library/hh286405%28v=vs.92%29.aspx in this link you can see the my code where i think i have the problem: http://pastebin.com/LYqzuqYb when i run app and click on button1 i have i have a Invalid Cast Error, i use the cast only in

    Category = (DB.Elements)listPicker.SelectedItem

but i don't undestand where is the problem best regads Antonio

More information i use this for insert element in listPicker

 public Inserimento()
    {
        InitializeComponent();
        List<Elenco> source = new List<Elenco>();
        source.Add(new Elenco() { Elemento = "Value1"});
        source.Add(new Elenco() { Elemento = "Value2" });
        source.Add(new Elenco() { Elemento = "Value3" });
        source.Add(new Elenco() { Elemento = "Value4" });
        this.listPicker.ItemsSource = source;
    }

Elemento is this class, i use this class for insert and store element in listPicker

namespace Example.ViewModel{
public class Elenco
{  public string Elemento
    {
        get;
        set;
    }

}}

Answer 1

When the Inserimento method is executed your listPicker contains a list of Elenco objects. Retrieving an item from that listPicker will retrieve one Elenco object. So this:

Category = (DB.Elements)listPicker.SelectedItem

Should actually be this:

Category = (Elenco)listPicker.SelectedItem