Earlier this month, Windows Apps Team recently announced .NET Standard 2.0, a common .NET Standard that works for all .NET based applications.
From the blog post:
.NET Standard is the set of APIs which work in all .NET implementations. A good way to think about it is how HTML5 is today. There are many different browsers which implement HTML parsing and rendering, but the HTML standard is the common glue that holds the web together and allows for interoperability.
.NET Standard was introduced in June of 2016 to bring consistency to the .NET ecosystem. With the .NET Framework, Xamarin & Mono, .NET Core and then UWP, there were many different implementations of .NET and it was very difficult to write code or a library that could work across all of them. Using .NET Standard, and the tooling in Visual Studio, makes it possible to build libraries and NuGet packages that work literally everywhere .NET runs.
With the addition of .NET Standard 2.0 support for UWP with the Fall Creators Update, .NET developers will be able to share code across all Windows 10 devices, in the cloud and through the rest of the .NET ecosystem. This will also make it easier to reuse existing WinForms and WPF code as many of the most frequently used APIs like DataSet/DataTable, and popularly requested APIs like SqlClient, are now part of .NET Standard 2.0.
You can download .NET Standard 2.0 and future releases here:
https://github.com/dotnet/standard