.NET Framework External Method Source Code

Question

Is there any way to see the source code for methods that are implemented externally in the .NET framework?

I know about Reference Source which is a great resource, however a lot of the core classes in the .NET framework are implemented externally (I assume in C++?).

For example I am very interested in the internal workings of of the class String but almost half of the methods are declared with the extern keyword including this[int index] which appears to actually hold the characters in the string.

Where can I find the source code for String.this[int index] or String.nativeCompareOrdinalEx(String strA, int indexA, String strB, int indexB, int count) and other externally implemented methods?

Also, is there a particular reason why so much of the core framework classes are implemented externally? Is it so that they could utilize existing code or for performance reasons or something else?

Answer 1

For the new, community, version you can dig in the github, that's where I found the implementation of decimal subtraction (or were I was pointed to by SO in fact)

CoreCLR / src

You have roslyn code there too:

Roslyn at Github