How to get which version of the .net framework SDK is running

In the bad old world before .net core/v4 I was struggling to figure out how to return the version of the .net framework code was using. This is my best effort so far. NB Assumes you’re references System.Core;

var references = System.Reflection.Assembly.GetExecutingAssembly().GetReferencedAssemblies();
var core = references.FirstOrDefault(r => r.Name == "System.Core");
var sdkVersion = core.Version.ToString();