c#: WebBrowser控件html代码注入及交互

主题仍是下载相关。

页面加载完成后，注入html元素，以使能够与主程序交互。并使WebBrowser与js交互，可以实现一些有趣的功能。

欲使WebBrowser与js交互，其所在页面类，须加上[ComVisible(true)]标记。

记录嵌入代码如下：

    [ComVisible(true)]
    public partial class Main : Form
    {
        public Main()
        {
            InitializeComponent();
 
            browser.ObjectForScripting = this;
        }
 
        private void txtUrl_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
                btnGo.PerformClick();
        }
 
        private void btnGo_Click(object sender, EventArgs e)
        {
            if (!string.IsNullOrEmpty(txtUrl.Text))
                browser.Navigate(txtUrl.Text);
        }
 
        public void ShowURL(string url)
        {
            MessageBox.Show("OK, Url from website is:\r\n" + url, "Information", MessageBoxButtons.OK, MessageBoxIcon.Information);
        }
 
        private void browser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
        {
            if (browser.ReadyState == WebBrowserReadyState.Complete && e.Url == browser.Url)
            {
                //html注入
                var emt = browser.Document.GetElementById("movie_player"); //"watch-header");
                if (emt != null)
                {
                    Console.WriteLine("Yeah!");
                    //https://www.youtube.com/watch?v=vvppaufeD3Q
                    string style = "width:80px; height:24px; background-color:#99b4d1; float:right; text-align:center; line-height:24px;";
                    string imgData = "data:image/png;base64,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";
                    emt.OuterHtml = emt.OuterHtml + "\r\n<div onmouseover=\"this.style.backgroundColor='#799cc4'\" onmouseout=\"this.style.backgroundColor='#99b4d1'\" style=\"" + style + "\"><a onclick=\"window.external.ShowURL(location.href);return false;\"><img src=" + imgData+ " align=\"center\" />Click Me!</a></div>";
 
                   //用下面方法，在有些网站上，其js不能被执行，而上面追加OuterHtml可以 
                   //var ne = browser.Document.CreateElement("div");
                   //ne.SetAttribute("style", style);
                   //ne.InnerHtml = "<div style=\"" + style + "\"><a onclick=\"window.external.ShowURL(location.href);return false;\"><img src=" + imgData + " align=\"center\" />Click Me!</a></div>";
                   //emt.InsertAdjacentElement(HtmlElementInsertionOrientation.AfterEnd, ne);
                }
            }
        }

效果如图：

颇是有点意思！

而WebBrowser没有Document所用的getElementsByClassName方法，以c#之扩展方法实现之，更为易用：

public static class ClassHelper
{
    public static List<HtmlElement> GetElementsByClassName(this HtmlDocument doc, string className)
    {
        var result = new List<HtmlElement>();
        foreach (HtmlElement emt in doc.All)
        {
            if (emt.GetAttribute("className") == className)
                result.Add(emt);
        }
 
        return result;
    }
}

参考：

C#中webbrowser与javascript(js)交互的方法 - DragonDean - 博客园