stringsandbeyond
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Using WebBrowser2 Interface in Multithreaded application.
david_johns and I are working on an application together. I had more points available so I am repeating his question with more points to hopefully attract an answer:
We are using a WebBrowser2 interface to do some work for us in our application. We are trying to introduce multithreading allowing the browser to pick up information in the background and let the user continue using the application.
We seem to lose control of the WebBrowser2 (it will no longer navigate or recieve when one thread that was using it exits and another tries to access it. The browser is still running, but the WebBrowser2 seems to be a corrupt pointer.
500 points for the person who can figure out how to acess the same WebBrowser2 interface inside of a thread different from the one it was created in or somehow store a reference to the browser itself from which we can restore the WebBrowser2 interface before starting to use it in the second thread. Thanks for your help.
We are using a WebBrowser2 interface to do some work for us in our application. We are trying to introduce multithreading allowing the browser to pick up information in the background and let the user continue using the application.
We seem to lose control of the WebBrowser2 (it will no longer navigate or recieve when one thread that was using it exits and another tries to access it. The browser is still running, but the WebBrowser2 seems to be a corrupt pointer.
500 points for the person who can figure out how to acess the same WebBrowser2 interface inside of a thread different from the one it was created in or somehow store a reference to the browser itself from which we can restore the WebBrowser2 interface before starting to use it in the second thread. Thanks for your help.
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>>Does this approach seem reasonable?
Hum, there is no need to multiply call 'CoInitializeEx()' - just do that once when your application starts up or creates a thread (then you need to call it agin in the new thread). Also, there is no need to pass the WebBrowser2 'back' again, once it is marshalled across the thread boundaries, both threads can use it. Just be sure to release the interface in both threads, so the proxy (if any) can be released by the marshaling layer.
>>Will the method crash if the thread that calls CoMarshalInterThreadInterf
>>exits before the interface is passed into the next thread that uses it?
I'd create the interface in the applications main thread and pass it to the others when they 'need' it.
BTW, if you want to avoid all the marshalling hassle, take a look at http://msdn.microsoft.com/library/default.asp?url=/library/en-us/com/htm/cmi_d2l_5omd.asp ("IGlobalInterfaceTable"),
Hum, there is no need to multiply call 'CoInitializeEx()' - just do that once when your application starts up or creates a thread (then you need to call it agin in the new thread). Also, there is no need to pass the WebBrowser2 'back' again, once it is marshalled across the thread boundaries, both threads can use it. Just be sure to release the interface in both threads, so the proxy (if any) can be released by the marshaling layer.
>>Will the method crash if the thread that calls CoMarshalInterThreadInterf
>>exits before the interface is passed into the next thread that uses it?
I'd create the interface in the applications main thread and pass it to the others when they 'need' it.
BTW, if you want to avoid all the marshalling hassle, take a look at http://msdn.microsoft.com/library/default.asp?url=/library/en-us/com/htm/cmi_d2l_5omd.asp ("IGlobalInterfaceTable"),
BTW, on the last issue, see also
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/com/htm/aptnthrd_4ew5.asp ("Creating the Global Interface Table")
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/com/htm/aptnthrd_6uat.asp ("When to Use the Global Interface Table")
http://www.microsoft.com/msj/0997/activex0997.aspx ("ActiveX Q&A, MSJ September, 1997 - Apartment Neutrality: The Free Threaded Marshaler and the Global Interface Table")
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/com/htm/aptnthrd_4ew5.asp ("Creating the Global Interface Table")
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/com/htm/aptnthrd_6uat.asp ("When to Use the Global Interface Table")
http://www.microsoft.com/msj/0997/activex0997.aspx ("ActiveX Q&A, MSJ September, 1997 - Apartment Neutrality: The Free Threaded Marshaler and the Global Interface Table")
ASKER
jkr,
You're the best! Thanks again.
You're the best! Thanks again.
ASKER
Wow! Thanks for all the great info. Just one more question before I close this out. As David mentioned we have developed a class that attempts to make the process of using the browser really easy. As of yet the class does not have any knowledge about the thread that creates it and the one that is operating it.
I am guessing that the best way to handle it is to create the browser instance in the first thread that needs it and go ahead and call CoMarshalInterThreadInterf
Thanks so much for your help.