Check the path to the database, since you don't specify any in your connections string:
static string _ConnectionString = @"Data Source=VacDB;Version=3;New=False;Compress=True";
the file will be loaded from the current directory, which may not be the same as the folder you expect - remember that C# projects generally have at least two binary folders: bin/debug and bin/release so you may be reading the wrong one.
In any case, it's a bad idea to keep your data with your executable: in production the app will be installed under "Program Files" which is read only without admin access in modern OSes, so what works in dev, can fail in prod. See here:
Where should I store my data?[
^] - it shows some safer places to keep it.