Picking up and saving a contact in windows phone 7 app

I have tried to choose contact from contact list in windows phone 7 app and I display it in a textbox. Now I want to save that contact in that textbox for future use of that application. How I can save a chosen contact from a windows phone in a text box. This is the code I tried.
PhoneNumberChooserTask phoneNumberChooserTask;

phoneNumberChooserTask = new PhoneNumberChooserTask();

phoneNumberChooserTask.Completed += phoneNumberChooserTaskOnCompleted;

phoneNumberChooserTask.Show();

private void phoneNumberChooserTaskOnCompleted(object sender, PhoneNumberResult phoneNumberResult)

{

if (phoneNumberResult.TaskResult == TaskResult.OK)

{ textBox1.Text = phoneNumberResult.PhoneNumber; }

 }