1、Your project.json doesn't list 'win' as a targeted runtime. You should add '"win": { }' inside your "runtimes" section in your project.json, and then re-run NuGet restore.

解决方法：

• Clean solution
• Delete obj folders
• Delete the .vs folder (optional)
• Close and reopen Visual Studio
• Then build
• 如果还不行的话，再试试这个：It turns out that NuGet had snuck in a project.lock.json. Once I deleted the file, the problem went away.
• 如果分开试不行，全部步骤一起上，我是全部一起都用了才行的（甚至把bin目录也删了）。