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
objfolders - Delete the
.vsfolder (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）。