C# webbrowser判断页面是否加载完毕

private void Form1_Load(object sender, EventArgs e)
{
webalipay.Url = new Uri("https://authzth.alipay.com/login/homeB.htm");
webalipay.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(wb_DocumentCompleted);//加载完成后的事件
}
/// <summary>
/// 页面加载完事件
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void wb_DocumentCompleted(object sender, EventArgs e)
{
//这个就是当网页载入完毕后要进行的操作
hdoc = webalipay.Document;
HtmlElement imgcode = Function.WebTools.GetElement_Id(hdoc, "J-checkcode-img");
codeurl = imgcode.GetAttribute("src");
piccode.Imagelocatio{过滤}n = codeurl;
}