public filepath,filter;
private void createwatch(FileSystemWatcher watchclass,string path,string filter)
{
watchclass = new FileSystemWatcher(path,filter);
watchclass.Created += new FileSystemEventHandler(watchclass_Created);
watchclass.EnableRaisingEvents = true;
}
private void button2_Click(object sender, System.EventArgs e)
{
if(button2.Text=="开始监视")
{
createwatch(new FileSystemWatcher(),filepath,filter);
button2.Text="停止监视";
}
else
{
                                     ???结束这个监视
}

}