在C#中，你可以使用異常處理來處理Watcher可能遇到的異常情況。以下是一個基本的示例，展示了如何在Watcher中處理異常：

using System;
using System.IO;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WatcherExample
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void btnStartWatcher_Click(object sender, EventArgs e)
        {
            btnStartWatcher.Enabled = false;
            btnStopWatcher.Enabled = true;

            Task.Run(() => StartWatcher());
        }

        private void btnStopWatcher_Click(object sender, EventArgs e)
        {
            btnStartWatcher.Enabled = true;
            btnStopWatcher.Enabled = false;
        }

        private void StartWatcher()
        {
            try
            {
                FileSystemWatcher watcher = new FileSystemWatcher();
                watcher.Path = @"C:\example_folder";

                watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite
                    | NotifyFilters.FileName | NotifyFilters.DirectoryName;

                watcher.Changed += new FileSystemEventHandler(OnChanged);
                watcher.Created += new FileSystemEventHandler(OnChanged);
                watcher.Deleted += new FileSystemEventHandler(OnChanged);
                watcher.Renamed += new RenamedEventHandler(OnRenamed);

                watcher.EnableRaisingEvents = true;

                Console.WriteLine("Watcher started.");
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error: " + ex.Message);
            }
        }

        private void OnChanged(object source, FileSystemEventArgs e)
        {
            // Handle the change event here.
            Console.WriteLine($"File '{e.FullPath}' has been changed.");
        }

        private void OnRenamed(object source, RenamedEventArgs e)
        {
            // Handle the rename event here.
            Console.WriteLine($"File '{e.OldFullPath}' has been renamed to '{e.FullPath}'.");
        }
    }
}

在這個示例中，我們創建了一個簡單的WinForms應用程序，其中包含一個開始Watcher按鈕和一個停止Watcher按鈕。當點擊開始按鈕時，會啟動一個新的Watcher任務，該任務將監視指定的文件夾。如果在啟動Watcher時發生任何異常，程序將彈出一個包含異常消息的對話框。