Simultaneously debug through intermediate language (IL) and C# in Visual Studio
What is your purpose? Is your IL generated by C# compiler or dynamically produced at run time? If the former one, you can use a trick of re-compiling your binary through ilasm.
- Compile C# code as you normally would. It does not matter if it is optimized or not, but you have to specify compilation option to produce full PDB symbols.
- Use ildasm to convert your binary to .il file. It is option Dump in the menu.
re-compile the .il file to get a new binary (and a new symbols)
ilasm .il [/exe|/dll] /debug
Now when debugging that specific assembly you will see IL code rather than C# code. You will also see a matching lines from original C# file if you select appropriate option in step 2.
For the case of dynamically generated IL, I would simply use WinDbg with SOS extension. It can dump IL and step through it, but it takes a bit to get used to.