Programmatically join Windows machine to AD domain

OK, here it is.

Firstly, the order of the fields in System Properties is a little misleading - you see Machine Name first, and Domain/Workgroup below that. This subconsciously affected my thinking, and meant my code copied that ordering by trying to set the name first, and then join the machine to the domain. Whilst this does work under some circumstances, it's not consistent or reliable. So the biggest lesson learned here is...

Join the domain first - then change the machine name.

Yep, that's actually all there is to it. After numerous test iterations, it finally dawned on me that it might work better if I tried it this way around. I tripped-up on the change of name on my first pass, but quickly realised that it was still using the local system credentials - but now that the machine was joined to the domain at this point, it needed the same domain credentials as were used to join the domain itself. A fast bit of code-tweaking later, and we now have a consistently-reliable WMI routine that joins the domain and then changes the name.

It might not be the neatest implementation (feel free to comment on improvements) but it works. Enjoy.

/// <summary>
/// Join domain and set Machine Name
/// </summary>
public static bool JoinAndSetName(string newName)
{
  _lh.Log(LogHandler.LogType.Debug, string.Format("Joining domain and changing Machine Name from '{0}' to '{1}'...", Environment.MachineName, newName));

  // Get WMI object for this machine
  using (ManagementObject wmiObject = new ManagementObject(new ManagementPath("Win32_ComputerSystem.Name='" + Environment.MachineName + "'")))
  {
    try
    {
      // Obtain in-parameters for the method
      ManagementBaseObject inParams = wmiObject.GetMethodParameters("JoinDomainOrWorkgroup");
      inParams["Name"] = "domain_name";
      inParams["Password"] = "domain_account_password";
      inParams["UserName"] = "domain_account";
      inParams["FJoinOptions"] = 3; // Magic number: 3 = join to domain and create computer account

      _lh.Log(LogHandler.LogType.Debug, string.Format("Joining machine to domain under name '{0}'...", inParams["Name"]));

      // Execute the method and obtain the return values.
      ManagementBaseObject joinParams = wmiObject.InvokeMethod("JoinDomainOrWorkgroup", inParams, null);

      _lh.Log(LogHandler.LogType.Debug, string.Format("JoinDomainOrWorkgroup return code: '{0}'", joinParams["ReturnValue"]));

      // Did it work?
      if ((uint)(joinParams.Properties["ReturnValue"].Value) != 0)
      {
        // Join to domain didn't work
        _lh.Log(LogHandler.LogType.Fatal, string.Format("JoinDomainOrWorkgroup failed with return code: '{0}'", joinParams["ReturnValue"]));
        return false;
      }
    }
    catch (ManagementException e)
    {
      // Join to domain didn't work
      _lh.Log(LogHandler.LogType.Fatal, string.Format("Unable to join domain '{0}'", _targetDomain), e);
      return false;
    }

    // Join to domain worked - now change name
    ManagementBaseObject inputArgs = wmiObject.GetMethodParameters("Rename");
    inputArgs["Name"] = newName;
    inputArgs["Password"] = "domain_account_password";
    inputArgs["UserName"] = "domain_account";

    // Set the name
    ManagementBaseObject nameParams = wmiObject.InvokeMethod("Rename", inputArgs, null);
    _lh.Log(LogHandler.LogType.Debug, string.Format("Machine Rename return code: '{0}'", nameParams["ReturnValue"]));

    if ((uint)(nameParams.Properties["ReturnValue"].Value) != 0)
    {
      // Name change didn't work
      _lh.Log(LogHandler.LogType.Fatal, string.Format("Unable to change Machine Name from '{0}' to '{1}'", Environment.MachineName, newName));
      return false;
    }

    // All ok
    return true;
  }
}