Left join between XML files in C#

[nemoOooZ]

Hi all,

I have two xml files and I need to export the result of applying a left outer join between them into a list

var result = from file1 in XDocument.Load(f1).Descendants("Contract")
             join file2 in XDocument.Load(f2).Descendants("Profile")
             on (file1.Element("CustomerAccID") != null ? file1.Element("CustomerAccID").Value : "")
             equals (file2.Element("Id") != null ? file2.Element("Id").Value : "")
             select new
             {
                ID = file1.Element("ID")!=null?file1.Element("ID").Value:"",
                EmployeeID = file1.Element("EmployeeID") != null ? file1.Element("EmployeeID").Value : "",
                Commision = file1.Element("Commision") != null ? file1.Element("Commision").Value : "",
                 Profile_Name = file2.Element("Profile_Name") == null ? "" : file2.Element("Profile_Name").Value,
            }; 

var list = result.ToList();

This code works as inner join not LEFT.
how to modify it to work as left, right, or full outer join?