get the primary domain controller (PDC)?

{

 The NetGetDCName function returns the name of the primary domain controller (PDC).

 It does not return the name of the backup domain controller (BDC) for the specified domain.

 Also, you cannot remote this function to a non-PDC server.

 Windows 2000/XP: Applications that support DNS-style names should call the  function.

 Domain controllers in this type of environment have a multi-master

 directory replication relationship.

 Therefore, it may be advantageous for your application to use a DC that is not the PDC.

 You can call the DsGetDcName function to locate any DC in the domain;

 NetGetDCName returns only the name of the PDC.

}

type

 EAccessDenied = Exception;

 EInvalidOwner = Exception;

 EInsufficientBuffer = Exception;

 ELibraryNotFound = Exception;

 NET_API_STATUS = Integer;

const

 NERR_Success = 0;

var

 NTNetGetDCName: function (Server, Domain: pWideChar; var DC: pWideChar): NET_API_STATUS; stdcall;

 NTNetGetDCNameA: function (Server, Domain: PChar; var DC: PChar): NET_API_STATUS; stdcall;

 NTNetApiBufferFree: function (lpBuffer: Pointer): NET_API_STATUS; stdcall;

procedure NetCheck(ErrCode: NET_API_STATUS);

begin

 if ErrCode <> NERR_Success then

 begin

   case ErrCode of

     ERROR_ACCESS_DENIED:

       raise EAccessDenied.Create('Access is Denied');

     ERROR_INVALID_OWNER:

       raise EInvalidOwner.Create('Cannot assign the owner of this object.');

     ERROR_INSUFFICIENT_BUFFER:

       raise EInsufficientBuffer.Create('Buffer passed was too small');

     else

       raise Exception.Create('Error Code: ' + IntToStr(ErrCode) + #13 +

         SysErrorMessage(ErrCode));

   end;

 end;

end;

function GetPDC(szSystem: string): string;

 { if szSystem = '' return the PDC else return DC for that domain }

const

 NTlib = 'NETAPI32.DLL';

 Win95lib = 'RADMIN32.DLL';

var

 pAnsiDomain: PChar;

 pDomain: PWideChar;

 System: array[1..80] of WideChar;

 ErrMode: Word;

 LibHandle: THandle;

begin

 Result := '';

 LibHandle := 0;

 try

   if Win32Platform = VER_PLATFORM_WIN32_NT then

   begin

     ErrMode := SetErrorMode(SEM_NOOPENFILEERRORBOX);

     LibHandle := LoadLibrary(NTlib);

     SetErrorMode(ErrMode);

     if LibHandle = 0 then

       raise ELibraryNotFound.Create('Unable to map library: ' +

         NTlib); @NTNetGetDCName := GetProcAddress(Libhandle, 'NetGetDCName');

       @NTNetApiBufferFree       := GetProcAddress(Libhandle,

       'NetApiBufferFree');

     try

       if szSystem <> '' then

         NetCheck(NTNetGetDCName(nil, StringToWideChar(szSystem, @System, 80), pDomain))

       else

         NetCheck(NTNetGetDCName(nil, nil, pDomain));

       Result := WideCharToString(pDomain);

     finally

       NetCheck(NTNetApiBufferFree(pDomain));

     end;

   end

   else

   begin

     ErrMode := SetErrorMode(SEM_NOOPENFILEERRORBOX);

     LibHandle := LoadLibrary(Win95lib);

     SetErrorMode(ErrMode);

     if LibHandle = 0 then

       raise ELibraryNotFound.Create('Unable to map library: ' +

         Win95lib); @NTNetGetDCNameA := GetProcAddress(Libhandle, 'NetGetDCNameA');

       @NTNetApiBufferFree := GetProcAddress(LibHandle, 'NetApiBufferFree');

     try

       if szSystem <> '' then

         NetCheck(NTNetGetDCNameA(nil, PChar(szSystem), pAnsiDomain))

       else

         NetCheck(NTNetGetDCNameA(nil, nil, pAnsiDomain));

       Result := StrPas(pAnsiDomain);

     finally

       NetCheck(NTNetApiBufferFree(pAnsiDomain));

     end;

   end;

 finally

   if LibHandle <> 0 then

   begin

     FreeLibrary(Libhandle); // free handle if it has been allocated

   end;

 end;

end;

// Example call, Beispielaufruf:

procedure TForm1.Button1Click(Sender: TObject);

begin

 try

   Screen.Cursor  := crHourGlass;

   label1.Caption := GetPDC('');

 finally

   Screen.Cursor := crDefault;

 end;

end;