How to detect if machine is joined to domain?

Question

How do I detect whether the machine is joined to an Active Directory domain (versus in Workgroup mode)?

Answer 1

You can check the PartOfDomain property of Win32_ComputerSystem WMI class. The MSDN says :

PartOfDomain

Data type: boolean

Access type: Read-only

If True, the computer is part of a domain. If the value is NULL, the computer is not in a domain or the status is unknown. If you unjoin the computer from a domain, the value becomes false.

/// 

/// Determines whether the local machine is a member of a domain.
/// 
/// A boolean value that indicated whether the local machine is a member of a domain.
/// http://msdn.microsoft.com/en-us/library/windows/desktop/aa394102%28v=vs.85%29.aspx
public bool IsDomainMember()
{
    ManagementObject ComputerSystem;
    using (ComputerSystem = new ManagementObject(String.Format("Win32_ComputerSystem.Name='{0}'", Environment.MachineName)))
    {
        ComputerSystem.Get();
        object Result = ComputerSystem["PartOfDomain"];
        return (Result != null && (bool)Result);
    }
}