wmi - Connecting DC Remote HyperV server in c# -

i trying connect hyperv server remotely part of same domain controller local system is. works if give username without ad, fails every time(with error "invalid parameter") when username ad.e.g. ad\administrator. // works

 impersonation = impersonationlevel.impersonate;  authority = "ntlmdomain:" + _domain;  options.username = "administrator";  options.password = _authpas; 

//but doesn't work

 impersonation = impersonationlevel.impersonate;  authority = "ntlmdomain:" + _domain;  options.username = "testad\\administrator";  options.password = _authpas; 

any highly appreciated.

why giving domain name in username after provided domain name in "authority"

already domain mentioned in authority the username should username without domainname

giving multiple times not work