USERNAME Function (DAX)
Returns the domain name and username from the credentials given to the system at connection time
Syntax
USERNAME()
Return Value
The username from the credentials given to the system at connection time
Remarks
Under Windows authentication, the returned string has the structure: <domain-name>\<user-name>
Example
The following code verifies if the user login is part of the UsersTable.
=IF(CONTAINS(UsersTable,UsersTable[login], USERNAME()), "Allowed", BLANK())