Disco.Services.DeviceExtensions.AssignDevice C# (CSharp) Method

        public static DeviceUserAssignment AssignDevice(this Device d, DiscoDataContext Database, User u)
        {
            DeviceUserAssignment newDua = default(DeviceUserAssignment);

            // Mark existing assignments as Unassigned
            foreach (var dua in Database.DeviceUserAssignments.Where(m => m.DeviceSerialNumber == d.SerialNumber && !m.UnassignedDate.HasValue))
                dua.UnassignedDate = DateTime.Now;

            if (u != null)
            {
                // Add new Assignment
                newDua = new DeviceUserAssignment()
                {
                    DeviceSerialNumber = d.SerialNumber,
                    AssignedUserId = u.UserId,
                    AssignedDate = DateTime.Now
                };
                Database.DeviceUserAssignments.Add(newDua);

                d.AssignedUserId = u.UserId;
                d.AssignedUser = u;
            }
            else
            {
                d.AssignedUserId = null;
            }

            // Update AD Account
            if (ActiveDirectory.IsValidDomainAccountId(d.DeviceDomainId))
            {
                var adMachineAccount = ActiveDirectory.RetrieveADMachineAccount(d.DeviceDomainId);
                if (adMachineAccount != null)
                    adMachineAccount.SetDescription(d);
            }

            return newDua;
        }