StyleCopAutoFix is a console application that will automatically fix StyleCop violations related to missing (or unnecessary) empty lines. It is free an open-source.
While the scope of the violations it fixes is fairly limited, it fix them in a safe way (it is unlikely it will break your code or change the behavior). These violations are also the most common ones.
If you use Visual Studio, I also recommend to run this script : https://gist.github.com/JayBazuzi/9e0de544cdfe0c7a4358. It automatically auto format all code of all files in a solution.
On projects I ran this application (and the VS script above) it fixes up to 60% of all violations.
Disclaimer : I am the author of this.
