EDIT: This answer was correct at the time of posting. In Windows Phone 7.1 (Mango) third-party applications will have access to contacts.
You can't. You're not allowed to. That's viewed as private data that applications shouldn't be touching.
EDIT: Although you can't directly access the contacts list, you can launch the EmailAddressChooserTask
or PhoneNumberChooserTask
to get back just that piece of information about a user-specified contact. (Likewise you can launch a task to save a phone number or email address.)
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…