CrossFrameIE UnauthorizedAccessException

CrossFrameIE

// FREE code from CODECENTRIX
// http://www.codecentrix.com/
// http://codecentrix.blogspot.com/
using System;
using System.Runtime.InteropServices;
using mshtml;


namespace CodecentrixSample
{
    public class CrossFrameIE
    {
        // Returns null in case of failure.
        public static IHTMLDocument2 GetDocumentFromWindow(IHTMLWindow2 htmlWindow)
        {
            if (htmlWindow == null)
            {
                return null;
            }

            // First try the usual way to get the document.
            try
            {
                IHTMLDocument2 doc = htmlWindow.document;
                return doc;
            }
            catch (COMException comEx)
            {
                // I think COMException won't be ever fired but just to be sure ...
                if (comEx.ErrorCode != E_ACCESSDENIED)
                {
                    return null;
                }
            }
            catch (System.UnauthorizedAccessException)
            {
            }
            catch
            {
                // Any other error.
                return null;
            }

            // At this point the error was E_ACCESSDENIED because the frame contains a document from another domain.
            // IE tries to prevent a cross frame scripting security issue.
            try
            {
                // Convert IHTMLWindow2 to IWebBrowser2 using IServiceProvider.
                IServiceProvider sp = (IServiceProvider)htmlWindow;

                // Use IServiceProvider.QueryService to get IWebBrowser2 object.
                Object brws = null;
                sp.QueryService(ref IID_IWebBrowserApp, ref IID_IWebBrowser2, out brws);

                // Get the document from IWebBrowser2.
                SHDocVw.IWebBrowser2 browser = (SHDocVw.IWebBrowser2)(brws);

                return (IHTMLDocument2)browser.Document;
            }
            catch
            {
            }

            return null;
        }

        private const int  E_ACCESSDENIED      = unchecked((int)0x80070005L);
        private static Guid IID_IWebBrowserApp = new Guid("0002DF05-0000-0000-C000-000000000046");
        private static Guid IID_IWebBrowser2   = new Guid("D30C1661-CDAF-11D0-8A3E-00C04FC9E26E");
    }

    // This is the COM IServiceProvider interface, not System.IServiceProvider .Net interface!
    [ComImport(), ComVisible(true), Guid("6D5140C1-7436-11CE-8034-00AA006009FA"),
    InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IServiceProvider
    {
		    [return: MarshalAs(UnmanagedType.I4)][PreserveSig]
		    int QueryService(ref Guid guidService, ref Guid riid, [MarshalAs(UnmanagedType.Interface)] out object ppvObject);
    }
}