如果您指的多个文件夹都在同一个文件夹中,那么属性this.fileSystemWatcher1.IncludeSubdirectories = true;//包含对子文件夹的监控
   如果在不同文件夹中,就多设置几个filesystemWatcher就对了//呵呵我的想法
   还有changed函数是有的,我是这么调用的:
private void fileSystemWatcher1_Changed(object sender, System.IO.FileSystemEventArgs e)
{
Console.WriteLine("File: " +  e.FullPath + " " + e.ChangeType);
MessageBox.Show("File: " +  e.FullPath + " " + e.ChangeType);//成功
}

   下面是我做的一个例子,希望对你有用
private void InitializeComponent()
{   
this.fileSystemWatcher1 = new System.IO.FileSystemWatcher();
this.label1 = new System.Windows.Forms.Label();
((System.ComponentModel.ISupportInitialize)(this.fileSystemWatcher1)).BeginInit();
this.SuspendLayout();
// 
// fileSystemWatcher1
// 
this.fileSystemWatcher1.EnableRaisingEvents = true;//开始监控
this.fileSystemWatcher1.IncludeSubdirectories = true;//包含对子文件夹的监控
this.fileSystemWatcher1.NotifyFilter = ((System.IO.NotifyFilters)((((System.IO.NotifyFilters.FileName | System.IO.NotifyFilters.DirectoryName) 
| System.IO.NotifyFilters.LastWrite) 
| System.IO.NotifyFilters.LastAccess)));//被监控的属性
this.fileSystemWatcher1.Path = "C:\\Documents and Settings\\Administrator\\My Documents";//设置被监控的文件夹
this.fileSystemWatcher1.SynchronizingObject = this;
this.fileSystemWatcher1.Deleted += new System.IO.FileSystemEventHandler(this.fileSystemWatcher1_Changed);
this.fileSystemWatcher1.Changed += new System.IO.FileSystemEventHandler(this.fileSystemWatcher1_Changed);
this.fileSystemWatcher1.Created += new System.IO.FileSystemEventHandler(this.fileSystemWatcher1_Changed);