Possible enumeration values:

NameValueDescription
SerialNumber

1

Sort by serial number ascending
SerialNumberDesc

-1

Sort by serial number descending
RegistrationDate

2

Sort by registration date ascending
RegistrationDateDesc

-2

Sort by registration date descending
SentByUser

4

Sort by sent by user ascending
SentByUserDesc

-4

Sort by sent by user descending
CreateDate

5

Sort by create date ascending
CreateDateDesc

-5

Sort by create date descending
LastUpdateDate

6

Sort by last update date ascending
LastUpdateDateDesc

-6

Sort by last update date descending