C# 5.0 is out now since August 2012. Where can I find the specification? They've stopped doing ECMA specs, but how about MSDN?
If you have Visual Studio 2012 installed, you will find specification somewhere there:
c:\Program Files (x86)\Microsoft Visual Studio 11.0\VC#\Specifications\1033\CSharp Language Specification.docx
similar with VS2013:
c:\Program Files (x86)\Microsoft Visual Studio 12.0\VC#\Specifications\1033\CSharp Language Specification.docx
VS2015:
c:\Program Files (x86)\Microsoft Visual Studio 14.0\VC#\Specifications\1033\CSharp Language Specification.docx