I have a .NET method which is marked as an "Internal Call", meaning that it is implemented within the CLR itself. Is there any way to locate the code for and/or decompile such a method?
If you use the windbg sos extension you can step into the internal calls - which are unmanaged code. The documentation for using sos is a bit tricky to sort out IMO. This link is helpful for learning the sos commands: http://msdn.microsoft.com/en-us/library/bb190764(v=vs.110).aspx. To load SOS I use:
.loadby sos clr ; for .NET 4 and higher .loadby sos mscorwks ; for .NET 2
However you have to wait until the .NET DLLs have been loaded before those commands work, so you either have to set a breakpoint or make sure the managed code has some kind of wait (for input or something else) to allow the process to load the .NET DLLs.