I was trying to install the package `Microsoft.AspNetCore.Http` from NuGet via MonoDevelop on Linux, and then I got this error:
The 'System.Text.Encodings.Web 4.0.0' package requires NuGet client version '2.12' or above, but the current NuGet version is '184.108.40.206'.
I don't see a way to update NuGet. I tried to file an issue over on NuGet's GitHub tracker, but they told me to file it here (link: https://github.com/NuGet/Home/issues/3382)
MonoDevelop 6.0.2 includes NuGet 2.12. That version is currently only available if you build MonoDevelop from GitHub.
If you are MonoDevelop 5.10 then you may be able to just replace the NuGet binaries in the /usr/lib/monodevelop/AddIns/MonoDevelop.PackageManagement directory. The NuGet 2.12 binaries are available from GitHub:
The Microsoft.Web.XmlTransform.dll and NuGet.Core.dll files are the ones used by MonoDevelop.