How to detect if machine is joined to domain?

Don't fool with pinvoke if you don't have to.

Reference System.DirectoryServices, then call:

System.DirectoryServices.ActiveDirectory.Domain.GetComputerDomain()

Throws an ActiveDirectoryObjectNotFoundException if the machine is not domain-joined. The Domain object that's returned contains the Name property you're looking for.

You can PInvoke to Win32 API's such as NetGetDcName which will return a null/empty string for a non domain-joined machine.

Even better is NetGetJoinInformation which will tell you explicitly if a machine is unjoined, in a workgroup or in a domain.

Using NetGetJoinInformation I put together this, which worked for me:

public class Test
{
    public static bool IsInDomain()
    {
        Win32.NetJoinStatus status = Win32.NetJoinStatus.NetSetupUnknownStatus;
        IntPtr pDomain = IntPtr.Zero;
        int result = Win32.NetGetJoinInformation(null, out pDomain, out status);
        if (pDomain != IntPtr.Zero)
        {
            Win32.NetApiBufferFree(pDomain);
        }
        if (result == Win32.ErrorSuccess)
        {
            return status == Win32.NetJoinStatus.NetSetupDomainName;
        }
        else
        {
            throw new Exception("Domain Info Get Failed", new Win32Exception());
        }
    }
}

internal class Win32
{
    public const int ErrorSuccess = 0;

    [DllImport("Netapi32.dll", CharSet=CharSet.Unicode, SetLastError=true)]
    public static extern int NetGetJoinInformation(string server, out IntPtr domain, out NetJoinStatus status);

    [DllImport("Netapi32.dll")]
    public static extern int NetApiBufferFree(IntPtr Buffer);

    public enum NetJoinStatus
    {
        NetSetupUnknownStatus = 0,
        NetSetupUnjoined,
        NetSetupWorkgroupName,
        NetSetupDomainName
    }

}

Can also be called by using system.net

string domain = System.Net.NetworkInformation.IPGlobalProperties.GetIPGlobalProperties().DomainName

If the domain string is empty the machine isn't bound.

Documentation on the property returned https://docs.microsoft.com/en-us/dotnet/api/system.net.networkinformation.ipglobalproperties.domainname?view=netframework-4.7.2#System_Net_NetworkInformation_IPGlobalProperties_DomainName

ManagementObject cs;
        using(cs = new ManagementObject("Win32_ComputerSystem.Name='" + System.Environment.MachineName + "'" ))
        {
            cs.Get();
            Console.WriteLine("{0}",cs["domain"].ToString());
        }

That should allow you to get the domain. I believe it will be null or empty if you are part of a workgroup and not a domain.

Make sure to reference System.Management

Just wanted to drop Rob's Code in VB:

 Public Class Test
    Public Function IsInDomain() As Boolean
        Try
            Dim status As Win32.NetJoinStatus = Win32.NetJoinStatus.NetSetupUnknownStatus
            Dim pDomain As IntPtr = IntPtr.Zero
            Dim result As Integer = Win32.NetGetJoinInformation(Nothing, pDomain, status)

            If (pDomain <> IntPtr.Zero) Then
                Win32.NetApiBufferFree(pDomain)
            End If

            If (result = Win32.ErrorSuccess) Then
                If (status = Win32.NetJoinStatus.NetSetupDomainName) Then
                    Return True
                Else
                    Return False
                End If
            Else
                Throw New Exception("Domain Info Get Failed")
            End If
        Catch ex As Exception
            Return False
        End Try
    End Function
End Class
Public Class Win32
    Public Const ErrorSuccess As Integer = 0
    Declare Auto Function NetGetJoinInformation Lib "Netapi32.dll" (ByVal server As String, ByRef IntPtr As IntPtr, ByRef status As NetJoinStatus) As Integer
    Declare Auto Function NetApiBufferFree Lib "Netapi32.dll" (ByVal Buffer As IntPtr) As Integer
    Public Enum NetJoinStatus
        NetSetupUnknownStatus = 0
        NetSetupUnjoined
        NetSetupWorkgroupName
        NetSetupDomainName
    End Enum
End Class

As Well as Stephan's code here:

Dim cs As System.Management.ManagementObject
    Try
        cs = New System.Management.ManagementObject("Win32_ComputerSystem.Name='" + System.Environment.MachineName + "'")
        cs.Get()
        dim myDomain as string = = cs("domain").ToString
    Catch ex As Exception
    End Try

I believe that only the second code will allow you to know what domain the machine joined, even if the current user IS NOT a domain member.

How to detect if machine is joined to domain?

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