CODEWITHSUNDEEP
c#asp.net.netvb.net
Hello-World
Hello-World

Reputation: 9555

call webbrowser control on code behind of asp.net page error?

How do you use a webbrowser control in code behind of a asp.net page. I get this error:

ActiveX control cannot be instantiated because the current thread is not in a single-threaded apartment.

thanks for the help

Imports System.Windows.Forms
Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.Web.UI.WebControls

Partial Class _Default

    Dim testcontrol As New WebBrowser() ' it breaks here

    Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load

        testcontrol.Navigate("mysite")

    End Sub

End Class

Upvotes: 1

Views: 2059

Answers (2)

Brian Hvarregaard
Brian Hvarregaard

Reputation: 4209

This is working:

/// <summary>
        /// Returns a thumbnail for the current member values
        /// </summary>
        /// <returns>Thumbnail bitmap</returns>
        protected Bitmap GetThumbnail()
        {
            try
            {
            // WebBrowser is an ActiveX control that must be run in a single-threaded
            // apartment so create a thread to create the control and generate the
            // thumbnail
            Thread thread = new Thread(new ThreadStart(GetThumbnailWorker));
            thread.SetApartmentState(ApartmentState.STA);
            thread.Start();
            thread.Join();
            return _bmp;
            }
            catch (Exception ex)
            {
                using (StreamWriter writer = new StreamWriter("log.txt", true))
                {
                    writer.WriteLine(string.Format("[{0}] {1}", DateTime.Now.ToString(), ex.ToString()));
                    writer.Flush();
                    writer.Close();
                }
                return null;
            }
        }


/// <summary>
        /// Creates a WebBrowser control to generate the thumbnail image
        /// Must be called from a single-threaded apartment
        /// </summary>
        protected void GetThumbnailWorker()
        {
            try
            {
                using (WebBrowser browser = new WebBrowser())
                {
                    browser.ClientSize = new Size(_width, _height);
                    //browser.ScrollBarsEnabled = false;
                    browser.ScriptErrorsSuppressed = true;
                    browser.Navigate(_url);
                    // Wait for control to load page
                    while (browser.ReadyState != WebBrowserReadyState.Complete)
                        Application.DoEvents();
                    // Render browser content to bitmap
                    _bmp = new Bitmap(_thumbWidth, _thumbHeight);
                    browser.DrawToBitmap(_bmp, new Rectangle(0, 0, _thumbWidth, _thumbHeight));
                }
            }
            catch (Exception ex)
            {
                using (StreamWriter writer = new StreamWriter("log.txt", true))
                {
                    writer.WriteLine(string.Format("[{0}] {1}", DateTime.Now.ToString(), ex.ToString()));
                    writer.Flush();
                    writer.Close();
                }
            }
        }

Upvotes: 0

Ann L.
Ann L.

Reputation: 13965

Why do you want to use WebBrowser behind the scenes in a ASP.NET app? If you need to interact with a web page on another server, usually people do that using HttpWebRequest.

Somebody out there can correct me if I'm wrong, but I believe a web app, almost by definition, cannot be single-threaded. Web apps are meant to be multi-user, to be doing multiple things and accommodating multiple users at once.

Upvotes: 1

Related Questions