Salesforce.SDK.Universal 5.0.0 

dotnet add package Salesforce.SDK.Universal --version 5.0.0
NuGet\Install-Package Salesforce.SDK.Universal -Version 5.0.0
This command is intended to be used within the Package Manager Console in Visual Studio, as it uses the NuGet module's version of Install-Package. 
<PackageReference Include="Salesforce.SDK.Universal" Version="5.0.0" />
For projects that support PackageReference, copy this XML node into the project file to reference the package. 
paket add Salesforce.SDK.Universal --version 5.0.0
#r "nuget: Salesforce.SDK.Universal, 5.0.0"
#r directive can be used in F# Interactive and Polyglot Notebooks. Copy this into the interactive tool or source code of the script to reference the package. 
// Install Salesforce.SDK.Universal as a Cake Addin
#addin nuget:?package=Salesforce.SDK.Universal&version=5.0.0

// Install Salesforce.SDK.Universal as a Cake Tool
#tool nuget:?package=Salesforce.SDK.Universal&version=5.0.0

The Salesforce SDK package is necessary for writing Salesforce applications on Windows. It contains the base features for OAuth, security, account management, and more. Support for windows 10 runtime included.

     Source: https://github.com/forcedotcom/SalesforceMobileSDK-Windows. Please follow the steps in https://github.com/forcedotcom/SalesforceMobileSDK-Windows/blob/master/README.md to install. You will need to use the template included in github in order to make use of this package initially; there are some setup steps that are needed that the template provides.

Product Compatible and additional computed target framework versions.
Universal Windows Platform uap was computed.  uap10.0 is compatible. 
Compatible target framework(s)
Included target framework(s) (in package)
Learn more about Target Frameworks and .NET Standard.

This package has no dependencies.

NuGet packages

This package is not used by any NuGet packages.

GitHub repositories

This package is not used by any popular GitHub repositories.

Version Downloads Last updated
5.0.0 3,207 12/17/2016
4.2.0 989 9/30/2016
4.0.0 1,153 12/6/2015