static string desktopPath = Environment.GetFolderPath(Environment.SpecialFolder.Desktop)+"/";

[STAThread]
static void Main( string[ ] args )
{
    //注册事件
    webBrowser.DocumentCompleted += WebBrowser_DocumentCompleted;

    webBrowser.Navigate( "https://helloareyouok.lanzous.com/i94vape" );

    Application.Run( );   
}

//事件调用
private static void WebBrowser_DocumentCompleted( object sender , WebBrowserDocumentCompletedEventArgs e )
{
    try
    {  
        MessageBox.Show( "加载成功" );

        WebBrowser webBrowser = (WebBrowser)sender;
        var 文件名 = webBrowser.Document.Title.Replace(" - 蓝奏云", "");
        
        // /html/body/div[2]/a
        HtmlElement a = webBrowser.Document.Window.Frames[0].Document.GetElementsByTagName("div")[1].FirstChild;
        //foreach( HtmlWindow item in webBrowser.Document.Window.Frames )
        //{
        //    var go = item.Document.GetElementById("go");
        //    a = go.FirstChild ?? null;
        //}
        var href = a.GetAttribute("href");
        MessageBox.Show( href );

        httpWebRequest = HttpWebRequest.CreateHttp( href );
      
        httpWebRequest.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";

        var uri=httpWebRequest.GetResponse().ResponseUri.ToString();

        Console.WriteLine( 文件名 );
        Console.WriteLine( uri );

        if( File.Exists( desktopPath + 文件名 ) )
        {
            File.Delete( desktopPath + 文件名 );
        }
        new WebClient().DownloadFile( uri , desktopPath + 文件名 );

    }
    finally
    {
        webBrowser.DocumentCompleted -= WebBrowser_DocumentCompleted;
    }
}