FileSystemWatcher 未调用更改事件

我写了下面的代码。

 [XmlRoot("myxml")]
public class myxml
{
    [XmlElement("one")]
    public string one { get; set; }
    [XmlElement("two")]
    public string two { get; set; }
}
class Program
{
    private static void OnChanged(object source, FileSystemEventArgs e)
    {
        // Specify what is done when a file is changed, created, or deleted.
        Console.WriteLine("File: " + e.FullPath + " " + e.ChangeType);
    }
  // 
    static void Main(string[] args)
    {
        myxml m = new myxml();
        m.one = "111";
        m.two = "222";
        FileSystemWatcher watcher = new FileSystemWatcher(@"c:'", "myxml.xml");
        watcher.Changed += new FileSystemEventHandler(OnChanged);
        FileStream fs = new FileStream(@"c:'myxml.xml", FileMode.Open);
        XmlSerializer x = new XmlSerializer(m.GetType());
        x.Serialize(fs, m);
        fs.Close();

    }
}

现在我认为在以下行之后将调用 OnChanged 事件，但没有......

x.Serialize(fs, m);

同样在这行之后什么也没发生

fs.Close();

知道吗？