A better way to wait for a variable to change state in VB.Net

Question

I have a loop that goes through a number of values. With every value iterated, a page is loaded in a webbrowser control (with the value passed as a parameter) and when the page

Answer 1

I've recently answered a similar question. The solution is in C#, but you can use Async/Await in VB.NET in a very similar way. Using this technique, you would get a natural flow of execution for your code (DocumentComplete event is encapsulated as Task).

Answer 2

One way would be to take whatever is after the loop, and put that in the handler for the control's DocumentComplete event.

Another would be to have this code run in another thread. It'd start the navigation and then wait on a semaphore, EventWaitHandle, or other waitable object that the DocumentComplete handler sets. Something like this:

private sem as Semaphore
private withevents wb as WebBrowser

...

sub DoWork()
    for each url as String in urls
        ' You'll almost certainly need to do this, since this isn't the UI thread
        ' anymore.
        wb.invoke(sub() wb.Navigate(url))
        sem.WaitOne()

        ' wb is done

    next
end sub

sub wb_DocumentComplete(sender as obj, args as WebBrowserDocumentCompletedEventArgs) _
handles wb.DocumentCompleted
    sem.Release()
end sub

...

dim th as new Thread(addressof me.DoWork)
th.Start()

Either way, since you're not taking up the UI thread anymore, you don't have to worry about Application.DoEvents().