C#写BHO时,在计时器中读webBrowse出错.

private System.Timers.Timer t = null;
WebBrowser webBrowse;
HTMLDocument document;
public void BHO_HelloWord()
{
   t = new System.Timers.Timer(1000);
   t.Elapsed += new System.Timers.ElapsedEventHandler(doit);
   t.AutoReset = true;
   t.Enabled = true;
   t.Start();
}
private void doit(object sender, EventArgs e) ///记时器
{
   MethodInvoker mi = new MethodInvoker(dw);
   this.BeginInvoke(mi); /// 标记1
   document = (HTMLDocument)webBrowse.Document;
   string abc = document.body.innerHTML;  ///标记2
}
public void OnDocumentComplete(object pDisp, ref object URL)
{
   document = (HTMLDocument)webBrowse.Document;
   string abc = document.body.innerHTML;   ///标记3
}

用C# 做 BHO的DLL
为什么,在DLL的类里不让用BeginInvoke委托?怎样解决? 标记1处
还有在计时器里读取webBrowse的内容(标记2处)会提示错误,无法使用COM控件,不能读取,而在

标记3处就正常. --------------------编程问答-------------------- 期待解答...顶 --------------------编程问答--------------------

补充：.NET技术 ,  C#