There are elements of truth in this, but it is not the whole story. While Silverlight did produce the first portable version of .NET and produces a lot of the

There are elements of truth in this, but it is not the whole story. While Silverlight did produce the first portable version of .NET and produces a lot of the code that allowed .NET to be portable, this code has been now retrofitted into the main CoreCLR and the VM source code has been upgraded. What you see in the public CoreCLR is now the state of the art and while I do not know how the exact mechanics work, my understanding is that the CoreCLR and the .NET Desktop VM that ships source codes are very close to each other - modulo branches, deliverables, freeze dates and other loose ends. On the library front, there has been a lot of rewriting for the sake of portability, cleaning up the code, and making the code more maintainable, and bringing it to the 2017 standards of coding.