How to capture screen shot image of website in IFRAME in ASP.Net

Ref:Capture Screenshot (Snapshot) Image of Website (Web Page) in ASP.Net using C# and VB.Net

Here i have added the iFrame in my page:

<form id="form1" runat="server">
    <asp:TextBox ID="txtUrl" runat="server" Text="" />
    <iframe id="iframeDemo" runat="server" src="http://aspsnippets.com/" height="500px"
        width="500px"></iframe>
    <asp:Button Text="Capture" runat="server" OnClick="Capture" />
    <br />
    <asp:Image ID="imgScreenShot" runat="server" Height="500" Width="700" Visible="false" />
    </form>

Src of IFram is http://aspsnippets.com/. So when i click on the button then it will take the Screen shot of the Src.

C#:

 protected void Capture(object sender, EventArgs e)
    {
        //string url = txtUrl.Text.Trim();
        string url = this.iframeDemo.Attributes["src"].ToString();
        Thread thread = new Thread(delegate()
        {
            using (WebBrowser browser = new WebBrowser())
            {
                browser.ScrollBarsEnabled = false;
                browser.AllowNavigation = true;
                browser.Navigate(url);
                browser.Width = 1024;
                browser.Height = 768;
                browser.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(DocumentCompleted);
                while (browser.ReadyState != WebBrowserReadyState.Complete)
                {
                    System.Windows.Forms.Application.DoEvents();
                }
            }
        });
        thread.SetApartmentState(ApartmentState.STA);
        thread.Start();
        thread.Join();
    }

    private void DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
    {
        WebBrowser browser = sender as WebBrowser;
        using (Bitmap bitmap = new Bitmap(browser.Width, browser.Height))
        {
            browser.DrawToBitmap(bitmap, new Rectangle(0, 0, browser.Width, browser.Height));
            using (MemoryStream stream = new MemoryStream())
            {
                bitmap.Save(stream, System.Drawing.Imaging.ImageFormat.Png);
                byte[] bytes = stream.ToArray();
                imgScreenShot.Visible = true;
                imgScreenShot.ImageUrl = "data:image/png;base64," + Convert.ToBase64String(bytes);
            }
        }
    }

In this i have commented TextBox value and use the Src value for taking Screen shot

Thank You.