Question

I’ve been having a bunch of exceptions when trying to use a WebBrowser on a multithread application. COM component, protected memory and other exceptions everywhere I do stuff with the WebBrowser. I just gave up and went back to my single thread version which works fine. I would post code but it’s hard to localize the cause of the problem when I get exceptions at so many spots. So, if as a single thread application it runs fine, and if when I run several instances of the same application it also works fine, there should be a way to simulate several applications running from a single application without having to actually make a separated application that I would run from the main application. My question, then, is how can I make Windows treat my threads as if they were different instances? This should eliminate the problem, since, as I said, when they ARE different instances I don’t get any exception. Hope I’m being clear enough.

Answer 1

I think your issue may have something to do with the way Microsoft.NET handles UI controls. Basically, any method for a control must be called from the thread that created it (perhaps even the main UI thread exclusively). Otherwise, you will get a bunch of access-related exceptions. I believe you will need to use the InvokeRequired property and Invoke method to call into the control, which also means that you will have to define a delgate function that wraps each method you want to call. Using the WebBroweser.Url property as an example, you could write something like this:

public delegate void SetWebAddressDelegate ( WebBrowser browser, Uri newUrl);

public void SetWebAddress ( WebBrowser browser, Uri newUrl )
{
    if (browser.InvokeRequired)
        browser.Invoke(new SetWebAddressDelegate(SetWebAddress), browser, newUrl);
    else
        browser.Url = newUrl;
}