Webbrowser獲取標籤的class的值

<pre name="code" class="csharp">//測試按鈕
        private void button2_Click(object sender, EventArgs e)
        {
            try
            {
                HtmlElementCollection Input = webBrowser1.Document.GetElementsByTagName("button");
                HtmlElementCollection Button = webBrowser1.Document.GetElementsByTagName("button");


                foreach (HtmlElement btn in Button)
                {
                    if (btn.GetAttribute("className").Equals("123")) //這裏當<button class="123" >的class="123"時
                    {
                        //去執行。。。。。
                        break;
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("結果："+ex);
            }
<span style="white-space:pre">	</span>}