c# - What does "Cannot evaluate expression because the code of the current method is optimized." mean?

Question

I wrote some code with a lot of recursion, that takes quite a bit of time to complete. Whenever I "pause" the run to look at what's going on I get:

Cannot evaluate expression because the code of the current method is optimized.

I think I understand what that means. However, what puzzles me is that after I hit step, the code is not "optimized" anymore, and I can look at my variables. How does this happen? How can the code flip back and forth between optimized and non-optimzed code?

Answer 1

While the Debug.Break() line is on top of the callstack you can't eval expressions. That's because that line is optimized. Press F10 to move to the next line - a valid line of code - and the watch will work.