Unable to install in nuget package

Question

I currently using VS2013, I'm using this for several months. I'm not encountering issue since then, but now I getting error. I unable to add package in my project.

The default XML namespace of the project must be the MSBuild XML namespace. If the project is authored in the MSBuild 2003 format, please add xmlns="http://schemas.microsoft.com/developer/msbuild/2003" to the element. If the project has been authored in the old 1.0 or 1.2 format, please convert it to MSBuild 2003 format. C:\project\NRMS\NRMS_Library\packages\EntityFramework.6.3.0\build\EntityFramework.props

I already add other package in this project last week, but now I'm encountering this issue. I do'nt want to mess up the current project because currently I have completed 50%. I already try create new project and try to install a package but getting same error.

Answer 1

Click Clear Package Cache under Tools --> Nuget Package Manager --> General

Or delete all files under C:\Users\xxx\AppData\Local\NuGet\Cache

Also , delete <solution_folder>\packages folder.

After that , restart your project and then run update-package -reinstall under Tools --> Nuget Package Manager --> Package Manager Console.

Answer 2

This thread may add some light, check it out: https://github.com/sendgrid/sendgrid-csharp/issues/482

In the 5th comment there's a guy recommending to get the code from an older version and provides the link.

Seems that an update changed the availability and caused the issue.