C# WebBrowser 抓图获取网页验证码

/// <summary>
/// 返回指定WebBrowser中图片<IMG></IMG>中的图内容
/// </summary>
/// <param name="WebCtl">WebBrowser控件</param>
/// <param name="ImgeTag">IMG元素</param>
/// <returns>IMG对象</returns>
private Image GetWebImage(WebBrowser WebCtl, HtmlElement ImgeTag)
{
    HTMLDocument doc = (HTMLDocument)WebCtl.Document.DomDocument;
    HTMLBody body = (HTMLBody)doc.body;
    IHTMLControlRange rang = (IHTMLControlRange)body.createControlRange();
    IHTMLControlElement Img = (IHTMLControlElement)ImgeTag.DomElement; //图片地址

    Image oldImage = Clipboard.GetImage();
    rang.add(Img);
    rang.execCommand("Copy", false, null);  //拷贝到内存
    Image numImage = Clipboard.GetImage();
    try
    {
        Clipboard.SetImage(oldImage);
    }
    catch
    {
    }

    return numImage;
}

//取得验证码
HtmlElement ImgeTag = webBrowser2.Document.All["id_randimage"];

Image numPic = GetWebImage(webBrowser2, ImgeTag); // 得到验证码图片
piccode.Image = numPic;