使用c#备份数据库,bak文件变得越来越大,如何阻止它增长？

这是我的代码

Server backFromServer = new Server(@"server ip add");
backFromServer.ConnectionContext.LoginSecure = false;
backFromServer.ConnectionContext.Login = "uname";
backFromServer.ConnectionContext.Password = "psd";
Database backFromDb = new Database();
backFromDb = backFromServer.Databases["dbname"];

Backup bkpDatabase = new Backup();
bkpDatabase.Action = BackupActionType.Database;
bkpDatabase.Database = backFromDb.Name;
bkpDatabase.Incremental = false;
bkpDatabase.LogTruncation = BackupTruncateLogType.Truncate;                

BackupDeviceItem bkpDevice = new BackupDeviceItem(@"D:backupfolderbackup.bak",DeviceType.File);

bkpDatabase.Devices.Add(bkpDevice);
bkpDatabase.SqlBackup(backFromServer);