how to bind webservice result to listbox

i want to display web service result in my list box but i getting the error
what is correct procedure for binding web service result to list box
following is the my code
public partial class Antocids : PhoneApplicationPage
{
ObservableCollection<Class1> p = new ObservableCollection<Class1>();


public Antocids()
{
InitializeComponent();
listBox1.DataContext = p;
ProductsClient client = new ProductsClient();
client.getProdDetailsCompleted += new EventHandler<getProdDetailsCompletedEventArgs>(client_getProdDetailsCompleted);
client.getProdDetailsAsync();
}
private void client_getProdDetailsCompleted(object sender, getProdDetailsCompletedEventArgs e)
{


// foreach (var result in e.Result)
//p.Add(result)//i tried this also but here also i got the error
foreach(Class1 r in e.Result)// here i got the error
p.Add(r);

}