更改excel文件数据时不会触发filesystemwatcher事件

Question

我创建了一个使用对象FileSystemWatcher的Web服务。现在当我尝试打开文件时，服务自动停止，否则filecreated方法正常工作。这是我的代码，

protected override void OnStart(string[] args)
{
        string dirname = @"C:\Users\Admin\Documents\Visual Studio 2017\WebSites\Project1\client";
        watch = new System.IO.FileSystemWatcher(dirname, "*.*");
        watch.Created += new FileSystemEventHandler(this.FileCreated);
        watch.Changed += new FileSystemEventHandler(this.FileChanged);
        watch.Deleted += new FileSystemEventHandler(this.FileDeleted);
        watch.Renamed += new RenamedEventHandler(this.FileRenamed);
        watch.IncludeSubdirectories = true;
        watch.EnableRaisingEvents = true;}

和filechanged方法就是这个 -

    public void FileChanged(object sender, FileSystemEventArgs e1)
    {
        MailMessage message = new MailMessage("***@gmail.com", "***@gmail.com");
        Attachment attachfile = new Attachment(e1.FullPath);
        message.Subject = "Data Changed " + e1.Name.ToString();
        message.IsBodyHtml = true;
        message.Body = "The Following File is  Changed " + Path.GetFileName(e1.FullPath.ToString()) + " in " + " at " + DateTime.Now.ToLongTimeString() + " by " + System.Environment.UserName.ToString();
        message.Attachments.Add(attachfile);
        SmtpClient smtp = new SmtpClient();
        smtp.Host = "smtp.gmail.com";
        smtp.EnableSsl = true;
        smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
        smtp.UseDefaultCredentials = false;
        System.Net.NetworkCredential credentials = new System.Net.NetworkCredential();
        credentials.UserName = "email@gmail.com";
        credentials.Password = "password";
        smtp.Credentials = credentials;
        smtp.Port = 587;
        smtp.Send(message);
        foreach (Attachment attachment in message.Attachments)
        {
            attachment.Dispose();
        }
    }

所以，请帮助我，即使我打开文件并更改其数据，如何继续运行Web服务。