How to Get the selected Item id in list box using Linq Query

Question

 var names = from s in dbc.Patient_Detail_Tables where s.Name.Contains(txtSearch.Text) select s;

            listBox1.DataSource = names;

            listBox1.DisplayMember = "Name";

            listBox1.ValueMember = "RegitrationNo";


How to get the valuemember using Linq query?