Visual studio 2013 evaluate expression problem

While debugging in vs 2013, you may run into the issue of the quick watch not evaluating the expressions while debugging. Try enabling Managed Compatibility mode by going to

Options --> Debugging --> General --> Use Managed Compatibility Mode

Note that this happened while debugging wcf services under windows 7 and never occurred on my machine running windows 8.1, but I may have been lucky.
Hope this save you some time and also check this blog post for more weird debug issues.