正如问题中已经提到的，重新安装Xamarin的所有内容也无法正常工作.卸载Visual Studio 2015即可.以下步骤可以解决问题(至少对我而言):

As already mentioned in the question, re-installing everything Xamarin also did not work. Uninstalling visual studio 2015 worked. The following steps did the trick (for me, at least):

1)卸载Visual Studio 2015 Beta.

1) Uninstall visual studio 2015 beta.

2)卸载Xamarin for Visual Studio.

2) Uninstall Xamarin for visual studio.

3)重新启动系统.

4)重新安装Xamarin Studio.现在，可以同时使用Xamarin Studio和VS2013进行编译.

4) Re-install Xamarin studio. Now, the compiles with both Xamarin studio as well as VS2013.

PS:这是这些最后解决方案之一.始终欢迎任何更好，更准确的答案.

PS: This is one of those last-resort solutions. Any better and more accurate answers are always welcome.