windows phone 发送短信

private void Appbar_Message_Click(object sender, EventArgs e)
        {
            SmsComposeTask composeSMS = new SmsComposeTask();
            var str = new StringBuilder();
            str.Append("【好消息】拍书网上的书籍《");
            str.Append(tblName.Text);
            str.Append("》只要" + tblPrice.Text);
            str.Append("元，点击" + UriContants.Domain + "/Book/Info/" + tblGuid.Text);
            str.Append(" 即可查看，赶快行动吧");
            composeSMS.Body = str.ToString();
            //composeSMS.To = "1765432548";
            composeSMS.Show();
        }