WPF Method to wait for DocumentCompleted Event

I know this has been asked before, but I don't think these solutions are flexible. The DocumentCompleted event should be used to determine when the load has completed, not as a method for performing work. If you need to perform several different tasks that each have to navigate several times, placing the logic in the DocumentCompleted event turns it into a messy switch/case router that is hard to read and maintain.

You need something that can actually wait during your method performing navigation so you can continue your task in the method you are already in. My first though is an actual Wait() method.

I would think something like this is close:

void WaitForLoad()
    {
        isLoading = true;
        while (isLoading)
        {
            if (Application.Current == null) break;
            Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Background, (DispatcherOperationCallback)delegate(object unused) { return null; }, null);
        }
    }

And set Isloading to false in the DocumentCompleted event.

You should be able to just call this method after whatever action will cause a pageload. It works, it has some issues.

1) it sends the CPU usage for the app up to 35% until the page has loaded, even if nothing else is happening.

2) if the application tries to close while its running, the loop will keep running and leave the app open with no windows, hence the need for the break when the app is null.

Can this be fixed, or am I coming at this all the wrong way?

Edit: I tried implementing the ManualResetEvent solution below, but it led to several other issues that I am not sure can be resolved without creating a messier situation than the one above. Since the WebBrowser is on the UI, locking the thread stop the entire app. If the work is done 开发者_如何学JAVAon the background thread it can be locked, but then accessing the WebBrowser becomes very difficult.

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In your situation, it sounds like you want a specific thread to block while waiting for the document to load. In that case, you would do something like this:

  protected ManualResetEvent _resetEvent = new ManualResetEvent(false);

  public void WaitingThread()
  {
      _resetEvent.WaitOne();

      // Do stuff after the web browser completes. 
  }

  public void LoadWebPage()
  {
      webBrowser.Navigate(new Uri(url));
      webBrowser.DocumentCompleted = (s, e) => { _resetEvent.Set(); };
  }

Basically, when the document completes, you signal the event and any threads waiting on the event unblock and continue executing.

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I noticed that you use Dispatcher.CurrentDispatcher.Invoke this is good for calling your method that somehow updates UI from another thread. But from code provided, I don't see any code in other thread then UI. So

1. Run that code on another thread.

2. On the close event of your application you can make isLoading=false; And more, if the method invoked is kind of long running stuff insert

   if(!isLoading) return;

   //or in some other app suitable way break an execution

EDIT:

Even better way to handle this in multithreading, then just simply relay on boolean variable, is using some Synchonization object