How do you programmatically determine whether a Windows computer is a member of a domain?

Question

I need a way to determine whether the computer running my program is joined to any domain. It doesn\'t matter what specific domain it is part of, just whether it is connecte

Answer 1

Here is a dead simple approach I don't see mentioned.

TCHAR UserDnsDomain[128] = { 0 }; 
DWORD Result = 0;

Result = GetEnvironmentVariable("USERDNSDOMAIN", UserDnsDomain, sizeof(UserDnsDomain));

if (Result == 0 || Result >= sizeof(UserDnsDomain) || GetLastError() == ERROR_ENVVAR_NOT_FOUND)
{
    return(FALSE); // Not logged in to a domain
}

This is predicated on the idea that if the user who is running this code is not currently logged in to a domain, then the USERDNSDOMAIN environment variable will be empty or unavailable. But there are some caveats you should think about.

Pros:

• Very easy to implement.
• 99% reliable.

Cons:

• May fail or return false results if the computer is domain joined, but the user executing this code is logged on to that computer with a local account.
• May fail or return false results if the computer is domain joined, but network connectivity to a domain controller was unavailable at the time of logon/user logged on with cached credentials.