Here is an example of using LINQ to return a List of all active Employees and their most current Mobile Phone number (if they have one). Check it out:

var query = (from emp in db.Employees
    where emp.IsActive
    let leftEmpPhone = db.EmployeePhones.Where(e => 
        e.EmployeeID == emp.EmployeeID &&  
        e.PhoneTypeID == (int)PhoneTypeEnum.Mobile)
        .OrderByDescending(e => e.CreateDate).FirstOrDefault()
    select new 
    {
         EmployeeID = emp.EmployeeID,
         EmployeeMobilePhoneNumber = leftEmpPhone == null 
                     ? "" 
                     : leftEmpPhone.PhoneNumber
    }).ToList();