VS生成解决方案时报错： Your project does not reference ".NETFramework,Version=v4.5"

 // 报错内容   
   Your project does not reference ".NETFramework,Version=v4.5" framework. Add a reference to ".NETFramework,Version=v4.5" in the "TargetFrameworks" property of your project file and then re-run NuGet restore. 

解决方法： 删除对应项目文件中的obj文件