1>------ 已启动生成: 项目: App6, 配置: Debug x86 ------
1>C:\Users\Administrator\documents\visual studio 2015\Projects\App6\App6\MainPage.xaml.cs(33,26,33,67): error CS0012: The type 'IAsyncAction' is defined in an assembly that is not referenced. You must add a reference to assembly 'Windows, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null, ContentType=WindowsRuntime'.
1>C:\Users\Administrator\documents\visual studio 2015\Projects\App6\App6\MainPage.xaml.cs(33,26,33,67): error CS0012: The type 'IAsyncActionWithProgress<>' is defined in an assembly that is not referenced. You must add a reference to assembly 'Windows, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null, ContentType=WindowsRuntime'.
1>C:\Users\Administrator\documents\visual studio 2015\Projects\App6\App6\MainPage.xaml.cs(33,26,33,67): error CS0012: The type 'IAsyncOperation<>' is defined in an assembly that is not referenced. You must add a reference to assembly 'Windows, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null, ContentType=WindowsRuntime'.
1>C:\Users\Administrator\documents\visual studio 2015\Projects\App6\App6\MainPage.xaml.cs(33,26,33,67): error CS0012: The type 'IAsyncOperationWithProgress<,>' is defined in an assembly that is not referenced. You must add a reference to assembly 'Windows, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null, ContentType=WindowsRuntime'.
测试了一下Win10的通用应用，结果莫名其妙就遇到了这个问题，资料翻了一下午，尝试了各种方法，没有发现什么可用的解决方案。
然后我在另一个没有装过VS2015的机器上直接安装VS2015+Win10SDK，同样的代码没有任何问题。
总结，你肯定之前安装过RC版本的VS2015，或者有卸载重装过VS2015。
希望刚开始折腾windows通用应用的同学，遇到这个问题不要浪费时间了！
请跟我一起重装系统吧！因为修复重装VS2015什么的都没用的！