The MSDN documentation on WebBrowser Customization explains how to prevent new windows from being opened and how to cancel navigation. In my case, my application is hosting an IWebBrowser2 but I don't want the user to navigate to new pages within my app. Instead, I'd like to open all links in a new IE window. The desired behavior is: user clicks a link, and a new window opens with that URL.
A similar question was asked and answered here and rather than pollute that answered post, it was suggested I open a new discussion.
The members on the related post suggested I should be able to do this by trapping DISPID_BEFORENAVIGATE2, setting the cancel flag, and writing code to open a new window, but I've found out that the browser control gets lots of BeforeNavigate2 events that seem to be initiated by scripts on the main page. For example, amazon.com fires BeforeNavigate2 events like crazy, and they are not a result of link invocation.
Replies appreciated!
What I ended up doing was using IHTMLDocument directly rather than IWebBrowser. IWebBrowser is a superset of IHTMLDocument, and the navigation model implemented by IWebBrowser isn't customizable to the degree I wanted.
I actually got MS Developer Support involved and this approach was their recommendation. They say this is what Outlook uses for HTML-based email, which is the user experience I wanted to emulate. They also confirmed that there's no reliable way to filter the OnBeforeNavigate events that result from user action from those that result from script activity.
Hope this helps anybody facing the same issues. It wasn't too hard to port the code to use IHTMLDocument. If you end up doing this, you may also find yourself looking for a way to figure out when the document is done loading. To do that, hook HTMLDocumentEvents instead of DWebBrowserEvents, and look for the DISPID_HTMLDOCUMENTEVENTS_ONREADYSTATECHANGE event. It doesn't tell you what the ready state is; you need to call IHTMLDocument::get_readyState and parse the resulting string. Goofy, but there you go.