/// <summary>
/// 跨域存取iframe
/// </summary>
///
/*
HtmlDocument main_formDoc = webBrowser1.Document;
IHTMLDocument2 main_mshtmlIHTMLDoc = (IHTMLDocument2)main_formDoc.DomDocument;
Object frame_index = 1;
IHTMLWindow2 target_mshtmlIHTMLWindow = (IHTMLWindow2)main_mshtmlIHTMLDoc.frames.item(ref frame_index);
IHTMLDocument2 target_mshtmlIHTMLDoc = CrossFrameIE.GetDocumentFromWindow(target_mshtmlIHTMLWindow);
*/
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);
}

跨域存取iframe