System.Data.SqlClient.SqlError: The tail of the log for the database "SlotMachineDBSQL" has not been backed up. Use BACKUP LOG WITH NORECOVERY to backup the log if it contains work you do not want to lose. Use the WITH REPLACE or WITH STOPAT clause of the RESTORE statement to just overwrite the contents of the log. (Microsoft.SqlServer.Smo)
Did you want to completely overwrite the database with the backup copy (and associated logs), or were you doing something a bit more exotic (page restore, filegoup restore, etc.)? If the former, then you just need to specify WITH REPLACE.