They may or may not use it involuntarily. It's a small chance scenario, but it's deffinitely one that happens. It usually happens with common names to like sqlConn or sqlCmd or strIN, ect ect. People use them and forget to declare them. Since the IDE sees them globally, it doesn't give them an error so they assume that they've already declared it. In actuallity, it's a global value that they're modifying and you (and the rest of your code) weren't planning on it.