Assets\Script\Facebooktop\fb.cs(230,36): error CS0246: The type or namespace name 'IAppInviteResult' could not be found

Question

Assets\Script\Facebooktop\fb.cs(230,36): error CS0246: The type or namespace name 'IAppInviteResult' could not be found (are you missing a using directive or an assembly reference?)

Here is the 230 line of the script:

private void AppInviteCallback(IAppInviteResult result)
{
    throw new NotImplementedException();
}