https://blog.faceutil.com/2017/10/10/xamarin-%ec%97%90%eb%ae%ac%eb%a0%88%ec%9d%b4%ed%84%b0-%ec%8b%a4%ed%96%89-%ec%96%b8%ec%96%b4-%eb%b0%8f-%ed%95%9c%ea%b8%80%ed%82%a4%eb%b3%b4%eb%93%9c-%ec%84%a4%ec%a0%95-%ce%bb/