how to get current user in event sink in share point server

[prem]

We are writing a code for EventSink, in the EventSink code, we need to
get the user name, the code we use to get the current

user name is:

Sharepointweb.currentUser.Name

when we use the above code, we always get the user name as 'NT
AUTHORITY\NETWORK SERVICES'.

We need the actual windows user name, kindly advice.

Thanks in advance for your efforts.