Installing a .NetStandard 2.0 Nuget package into a VS2015 Net 4.6.1 project

Referencing .NET Standard 2.0 packages is supported using the following:

• NuGet 3.6.0 or higher for VS 2015 (from NuGet's download site - may not yet be listed as recommended latest)
• Install the ".NET Standard Support for Visual Studio 2015" from https://aka.ms/netstandard-build-support-netfx (NuGet in VS will also print a link to this in its output window).

There are a still few bugs when consuming .NET Standard 2.0 libraries, especially when mixing .NET Standard < 2.0 and 2.0 libraries but these updates give basic support.

Is there any way to install a NetStandard 2.0 package into my project (without upgrading VS or installing any Net Core targeting packs or such)?

I am afraid not. Just like Jon pointed out that the reason for that issue is that you are using Visual Studio 2015.

According to the .NET Standard, .NET Standard 2.0 support .NET Framework 4.6.1 (with .NET Core 2.0 SDK):

So we need install .NET Core 2.0 SDK. And every communication from Microsoft about the preview of .NET Core 2.0 mentions Visual Studio 2017, so I think it's highly recommanded to use Visual Studio 2017 to work with .NET Core 2.0.

Besides, the NuGet package NETStandard.Library.NETFramework is deprecated.

So install a .NetStandard 2.0 Nuget package into a Net 4.6.1 project, I highly recommanded to use Visual Studio 2017 to work with .NET Core 2.0.

Hope this helps.