Solving NETSDK1061 build errors

Microsoft has changed a lot in the last 10 years, especially since Satya Nadella took over, and not for the better in many ways. One of the ways they've changed is that they've gotten a lot faster, which on the surface sounds good. When you start digging into the consequences of that change however, it's not so great: one of the ways in which that faster development velocity is enabled is by skipping over things I find to be essential, like documentation.

Today, the documentation that's missing from Microsoft's websites and negatively impacting me is how to keep the version of your dotnetcore 2.x+ SDKs "sticky" during your Visual Studio desktop builds and automated VSTS builds when Microsoft upgrades their SDKs. The very annoying thing is that Microsoft is going **so fast** that they're including beta and prerelease builds WITH VISUAL STUDIO!! That's a big no no as far as impacting one's customers in my book. The consequence of this is that you can upgrade Visual Studio, and what built with the previous version will no longer build with the current version. This results in builds errors with code:

NETSDK1061: The project was restored using Microsoft.NETCore.App version 2.1.3, but with current settings, version 2.1.3-servicing-26724-03 would be used instead. To resolve this issue, make sure the same settings are used for restore and for subsequent operations such as build or publish. Typically this issue can occur if the RuntimeIdentifier property is set during build or publish but not during restore. For more information, see https://aka.ms/dotnet-runtime-patch-selection.

Following the link in the error message, you're taken to documentation that tells you nothing useful about how to actually solve this error. Instead, you get to Google around and if you happen to find the right set of keywords and stumble across this documentation and read it **** VERY CAREFULLY **** you'll find that you need to make use of the "RuntimeFrameworkVersion" property that has to be specified in the .csproj project file of your dotnet core project, and you have to set that to the version you want to actually use for building your dotnet core project, in addition to a <PackageReference> element that looks similar to the following:

<PackageReference Update="Microsoft.NETCore.App" Version="2.1.2" />

The version in the above <PackageReference> element should match what you have in your <RuntimeFrameworkVersion> element.