Debugger stepping into if() block where condition is false

This is a known problem caused by the x64 jitter, it occasionally generates bad debug line number info. It can fumble when a statement causes extra NOPs instructions to be generated, intended to align code. The first NOP becomes the line number, instead of the instruction after the NOPs. This bytes in a few places, like a throw statement after a simple if() test and usage of the ?? operator with simple scalar operands. These alignment NOPs are also the reason why it is so dangerous to abort threads, described in this post.

Simplest workaround is Project + Properties, Build tab, tick the "Prefer 32-bit" option if available, set the Platform target to x86 otherwise. Note how nothing actually goes wrong, while the debugger suggests that the throw statement is going to be executed your program doesn't actually throw an exception.

It is being worked on, the x64 jitter was drastically rewritten, a project named RyuJIT. It will ship in VS2015, currently in Preview.

Check out this link. It's a known bug in some versions of visual studio and the .NET framework version. It's completely harmless and something you will just have to live with.