您应该访问PayPal网站并研究他们的文档。他们的SDK很可能只是为了通过他们的网站工作，所以你的桌面应用需要使用一些HTTP类来访问它。

You should go to the PayPal website and study their documentation. It is likely that their SDK is designed only to work through their website, so your Desktop app would need to use some HTTP classes to access it.