Why does my database not open? - windows-phone-8.1

Question

I am using SQLite in a windows 8.1 mobile app and when I am trying to delete something from the database I get an exception in the method RunInTransaction:
Cannot create commands from unopened database.
But when I try to insert something it works fine!
This is the insertion method:
// Inserts a new place in the Places table.
public void InsertPlace(PlacesTable place) {
using (var dbConn = new SQLiteConnection(App.DB_PATH)) {
dbConn.RunInTransaction(() => {
dbConn.Insert(place);
});
}
}
And this is the delete method:
// Deletes all the places from the database.
public void DeletePlaces() {
using (var dbConn = new SQLiteConnection(App.DB_PATH)) {
dbConn.RunInTransaction(() => {
dbConn.DropTable<PlacesTable>();
dbConn.CreateTable<PlacesTable>();
dbConn.Dispose();
dbConn.Close();
});
}
}
Why does this exception occur in the second case?
So, I found out that Dispose and Close were responsible for the exception, though I would like someone to explain me why this happened.
Was Close causing a problem because I had using (var dbConn = new SQLiteConnection(App.DB_PATH)) and Dispose for a similar reason?
I had found this at a tutorial, so it took me some time until I thought that the code had a mistake.