What is this?

This is a demonstration of an issue described in a stackoverflow question.

The Challenge

Make this solution build in VS2015 i.e. within the IDE, using Project > Build.

The solution can be built from the command line using:

msbuild /tv:12.0 /p:Platform="Any CPU" /p:Configuration=Debug

However, that's not the point. We need to be able to build it in the IDE.

What makes it fail?

There's a file, RequiredToolsVersion.targets, imported into toolsversion.csproj that will trigger a build error if it's built with a ToolsVersion other than 12.0.

Really, why?

See the question on stackoverflow.