What are these differences in two DLL file generated from the same source code
This might have something to do with differences between Build and a ReBuild
Difference between Build Solution, Rebuild Solution, and Clean Solution in Visual Studio?
if it doesn't think it needs to rebuild a project, it won't. It may also use partially-built bits of the project if they haven't changed
Performing a build uses metadata behind the scenes and thus your dll's can be different
Why is a different dll produced after a clean build, with no code changes?
You will need to perform a deterministic build as described here