procedure TIBConnection.ConnectFB;
var
  ADatabaseName: String;
  DPB: string;
begin
  DPB := chr(isc_dpb_version1);
  if (UserName <> '') then
  begin
    DPB := DPB + chr(isc_dpb_user_name) + chr(Length(UserName)) + UserName;
    if (Password <> '') then
      DPB := DPB + chr(isc_dpb_password) + chr(Length(Password)) + Password;
  end;
  if (Role <> '') then
     DPB := DPB + chr(isc_dpb_sql_role_name) + chr(Length(Role)) + Role;
  if Length(CharSet) > 0 then
    DPB := DPB + Chr(isc_dpb_lc_ctype) + Chr(Length(CharSet)) + CharSet;

  FSQLDatabaseHandle := nil;
  if HostName <> '' then ADatabaseName := HostName+':'+DatabaseName
    else ADatabaseName := DatabaseName;
  if isc_attach_database(@FStatus[0], Length(ADatabaseName), @ADatabaseName[1],
    @FSQLDatabaseHandle,
         Length(DPB), @DPB[1]) <> 0 then
    CheckError('DoInternalConnect', FStatus);
end;