Problem in BackUp

[C# Programming]

Hi to all,
I write below code to create backup
but it doesn't work

ServerConnection connection = new ServerConnection(".");
Server srv = new Server(connection);
SaveFileDialog sfd = new SaveFileDialog();
if (sfd.ShowDialog() == DialogResult.OK)
{
Backup bkpDatabase = new Backup();
bkpDatabase.Action = BackupActionType.Database;
bkpDatabase.Database = txtDBName.Text;//txtDBName contain Name of database
BackupDeviceItem bkpDevice = new BackupDeviceItem(sfd.FileName, DeviceType.File);
bkpDatabase.Devices.Add(bkpDevice);
bkpDatabase.SqlBackup(srv);
}//if