How to set a default value for attribute if it doesn't exist in the XDocument object

I am trying to load an xml file. I did this:

from e in XDocument.Load(stream).Root.Elements("cust")
                            select new Customer
                            {
                                MemeberID = (int)e.Attribute("custid"),
                                CustomerID = (int)e.Attribute("custid"),
                                FirstName = (string)e.Attribute("fname"),
                                LastName = (string)e.Attribute("lname"),
                                ShowsNumber = (int)e.Attribute("count_noshow"),
                                VisitNumber = (int)e.Attribute("count_resos"),
                                Cancellation = (int)e.Attribute("count_cancel"),
                                MobileNumber = (string)e.Element("phone").Attribute("phonenumber")
                            })

even thing was working good, but now i have a situation in which the xml document is not neccessary to have the mobilenuber attribute. so can I set a default value for this mobile number if it wasn't there in the xml node?

many thanks