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Invoke a javascript function in WebBrowser and wait until javascript event fires

I'm working in .NET, C# to be specific, creating a Win Forms UserControl, which contains a WebBrowser control. The WebBrowser control hosts a page, which in turn uses a third-party javascript component. The problem I'm having is with invoking a javascript function to initialize the third-party javascript component and block the UI in the Windows Forms application until the component has been initialized, which the component notifies you of through an internal javascript event that it has.
Part of the problem is that the only way to change any configuration parameter of the third-party javascript component is to re-initialize it with the new configuration. So for example, if you want to make it read-only you have to re-initialize it with the read-only parameter.
I've got everything working in terms of being able to call the Document.InvokeScript and then in the web page call the UserControl method using window.external but the problem I'm having is how to block the UserControl code that makes the call to initialize the javascript component so that it waits and doesn't return control to the user until the initialization of the javascript component has been completed.
The reason I need it to work this way is because if I have a "Read-Only" checkbox on the form that changes the the ReadOnly property of the UserControl to control whether the javascript component shows the data as read-only and the user clicks that checkbox really quickly you will either get a javascript error or the checkbox will get out of sync with the actual read-only state of the javascript component. This seems to happen because the control hasn't re-initialized yet after it's configuration has changed and you're already trying to change it again.
I've spent hours and hours trying work out a way to make it work using everything from AutoResetEvent to Application.DoEvents and so on, but don't seem to be able to get it working.
The closest I've found is Invoke a script in WebBrowser, and wait for it to finish running (synchronized) but that uses features introduced in VS2012 (and I'm using VS2010) and I don't think it would work anyway as it's a bit different in that you're not waiting for a javascript event to fire.
Any help would be greatly appreciated.

The problem in the first place is the requirement to "block" the UI thread until some event has been fired. It's usually possible to re-factor the application to use asynchronous event handlers (with or without async/await), to yield execution control back to the message loop and avoid any blocking.
Now let's say, for some reason you cannot re-factor your code. In this case, you'd need a secondary modal message loop. You'd also need to disable the main UI while you're waiting for the event, to avoid nasty re-entrancy scenarios. The waiting itself should to be user-friendly (e.g., use the wait cursor or progress animation) and non-busy (avoid burning CPU cycles on a tight loop with DoEvents).
One way to do this is to use a modal dialog with a user-friendly message, which gets automatically dismissed when the desired JavaScript event/callback has occured. Here's a complete example:
using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
namespace WbTest
{
[ComVisible(true)]
[ClassInterface(ClassInterfaceType.None)]
[ComDefaultInterface(typeof(IScripting))]
public partial class MainForm : Form, IScripting
{
WebBrowser _webBrowser;
Action _onScriptInitialized;
public MainForm()
{
InitializeComponent();
_webBrowser = new WebBrowser();
_webBrowser.Dock = DockStyle.Fill;
_webBrowser.ObjectForScripting = this;
this.Controls.Add(_webBrowser);
this.Shown += MainForm_Shown;
}
void MainForm_Shown(object sender, EventArgs e)
{
var dialog = new Form
{
Width = 100,
Height = 50,
StartPosition = FormStartPosition.CenterParent,
ShowIcon = false,
ShowInTaskbar = false,
ControlBox = false,
FormBorderStyle = FormBorderStyle.FixedSingle
};
dialog.Controls.Add(new Label { Text = "Please wait..." });
dialog.Load += (_, __) => _webBrowser.DocumentText =
"<script>setTimeout(function() { window.external.OnScriptInitialized}, 2000)</script>";
var canClose = false;
dialog.FormClosing += (_, args) =>
args.Cancel = !canClose;
_onScriptInitialized = () => { canClose = true; dialog.Close(); };
Application.UseWaitCursor = true;
try
{
dialog.ShowDialog();
}
finally
{
Application.UseWaitCursor = false;
}
MessageBox.Show("Initialized!");
}
// IScripting
public void OnScriptInitialized()
{
_onScriptInitialized();
}
}
[ComVisible(true)]
[InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
public interface IScripting
{
void OnScriptInitialized();
}
}
Which looks like this:
Another option (a less user-friendly one) is to use something like WaitOneAndPump from here. You'd still need to take care about disabling the main UI and showing some kind of waiting feedback to the user.
Updated to address the comment. Is your WebBrowser actually a part of the UI and visible to the user? Should the user be able to interact with it? If so, you cannot use a secondary thread to execute JavaScript. You need to do it on the main thread and keep pumping messages, but WaitOne doesn't pump most of Windows messages (it only pumps a small fraction of them, related to COM). You might be able to use WaitOneAndPump which I mentioned above. You'd still need to disable the UI while waiting, to avoid re-entrancy.
Anyhow, that'd still be a kludge. You really shouldn't be blocking the execution just to keep the linear code flow. If you can't use async/await, you can always implement a simple state machine class and use callbacks to continue from where it was left. That's how it used to be before async/await.

WebBrowser and Thread.Sleep oddity (default browser launched instead of WebBrowser control)

Okay, the goal is to attempt to detect when a web page has been updated, and display the updated page in a WebBrowser control. For instance, say that I know Amazon will make the Playstation 4 available today, but I don't know when. I put the address of the Amazon PS4 page in my form, and the program periodically launches a WebBrowser to that page and saves the HTML to a list of string. Next time around when it launches the browser, it will check the results against my list. If the list already contains this particular string, the WebBrowser is closed and we wait again using Thread.Sleep.
private void Launch()
{
while (blnWorking)
{
if (intWindowCount < intMaxCount)
{
ShowBrowserUri(GetBrowserUri());
}
if (intWait > 0)
Thread.Sleep(intWait);
}
}
delegate void ShowBrowserUriDelegate(Uri uri);
private void ShowBrowserUri(Uri uri)
{
if (InvokeRequired)
{
ShowBrowserUriDelegate del = new ShowBrowserUriDelegate(ShowBrowserUri);
Invoke(del, uri);
}
else
{
CookieContainer cc = GetUriCookieContainer(uri);
CookieCollection cc1 = new CookieCollection();
if (cc != null)
{
cc1 = cc.GetCookies(uri);
}
THBrowser thb = new THBrowser(uri, cc1, this); //THBrowser is a form with a WebBrowser control
//THBrowser calls the Navigate method of its WebBrowser control
intWindowCount++;
thb.Show();
thb.SendToBack();
}
}
The problem is, my program seems to be randomly opening the website in Firefox (my default browser) instead of using the THBrowser/WebBrowser. I've stepped through, and it seems to occur every time I step out of the Thread.Sleep.
It also may be relevant that OnDocumentComplete for my WebBrowser compares the current HTML to my List of HTML strings and closes the control if the page contents are already contained in my list.
I don't have the most recent version in front of me, but that part goes something like...
void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
if (e.Url.AbsolutePath != (sender as WebBrowser).Url.AbsolutePath)
return;
if (ResultsList.Contains(this.webBrowser1.Document.Body.InnerHtml)
this.Close();
else
ResultsList.Add(this.webBrowser1.Document.Body.InnerHtml);
}
I think this may be relevant because the THBrowser opens briefly, disappears, then a new tab is immediately opened in Firefox.
I'm pretty sure the Thread.Sleep has something to do with it. Although, I had seen this problem occasionally before introducing the Thread.Sleep, it has multiplied 100 fold since.
Maybe Thread.Sleep isn't the best way to space out my intervals. Maybe I'm just going about this completely wrong. Any suggestions are appreciated.

First, it's highly unlikely that Thread.Sleep has anything to do with the page sometimes loading in Firefox rather than in the WebBrowser control.
Thread.Sleep is not typically the best way to do things periodically. You'd probably be better off with a timer. If you're using Windows Forms, that's System.Windows.Forms.Timer. Set the Interval to whatever delay you want, and have the Tick event update the browser.
I'm not sure why you're creating a new WebBrowser control every time. Seems you'd be better off creating it just once and then calling Refresh method.
Finally, do you really need a WebBrowser? You might be better off just using WebClient.DownloadString to download the HTML.

Map.SetView() on Windows Phone 8

Is there a specific time in the page's lifecycle that the Map.SetView() function should be called? In our app we use this on various map objects and it seems to work randomly, sometimes perfectly and sometimes with no effect but also no exception.
example code:
RouteMap.SetView(LocationRectangle.CreateBoundingRectangle(DirectionCoordinates));
Where RouteMap is the mapping component and DirectionCoordinates contains the start/end coordinates for the map.
I can see that the bounding box is being created properly, but the map's positioning is not always being affected even loading the same data. If I add a break point it does seem to work, so I was assuming it had something to do with the map loading, but adding the SetView() functionality to the Loaded event has the same issue. We currently process the map information in the page Loaded event.
Update
I've been testing more and added events to what I could, I know for a fact that the MapLoaded event is being called before SetView. After SetView is called, it is working sometimes and not others. Neither ViewChanging or ViewChanged events are called.

This is obviously not the best solution, but there must be something that is not quite finished loading when the Loaded event is called that is preventing this from finishing.
I added a 100ms sleep to the Map_Loaded event and it has solved the problem I was having.
System.Threading.Thread.Sleep(500);
update
100ms isn't working for some people, you may want to play around with the numbers, 200, 500 etc. It's still a very short delay on the map's load time. I have contacted Microsoft about this and they have told me that they are looking into the issue and we will hopefully have some sort of response from them shortly.
update and edit
Use the following code instead to prevent UI hanging:
await Task.Delay(250);

I tackled this issue using ResolveCompleted event and boolean flag.
private void Map_ResolveCompleted(object sender, MapResolveCompletedEventArgs e)
{
if (this.zoomReq)
{
this.zoomReq = false;
if (this.locationList != null && this.locationList.Count > 0)
{
var viewRect = LocationRectangle.CreateBoundingRectangle(this.locationList);
this.Map.SetView(viewRect);
}
}
}
There is noticeable pause before map zooms but at least this seems to work all the time. The flag is needed because ResolveCompleted is fired every time the map moves.

I was both constructing a map layer (Microsoft.Phone.Maps.Controls.MapLayer) and setting the view (public void SetView(LocationRectangle boundingRectangle);) in an async method:
public async Task CreateMap()
{
map.Add(mapLayer);
map.SetView(locationRectangle);
}
I was doing some loading, that's why I used async.
This would only set the view once, the first time I navigated to the page.
The solution was to dispatch the set view call:
public async Task CreateMap()
{
map.Add(mapLayer);
Dispatcher.BeginInvoke(() =>
{
map.SetView(locationRectangle);
});
}
Hope that helps.

The Loaded event is the proper place for SetView(). You could try creating your rectangle in you OnNavigatedTo method. When I'm working with locations I always start my watcher in OnNavigatedTo and work with any map layers in _Loaded.

I worked myself some time at this problem. It didn't help to put most of the stuff to load into the constructor of the page. I tried to the trick with System.Threading.Thread.Sleep(500) but it took far beyond 500ms to take effect and this wasn't acceptable for me. For some people it helped to trigger an ZoomLevelChanged event and set the view in it. For myself I used a DispatcherTimer in which I used SetView() and fired an `ViewChanging´ event to stop the timer. If you use an animation the difference is pretty small.

I had this problem for MapAnimationKind.Linear but for MapAnimationKind.None it works without any problem
map.SetView(LocationRectangle.CreateBoundingRectangle(...), MapAnimationKind.None);

I had a very similar problem. Basically the setview of map would work the first time a page loaded (i.e. after all the data had finished loading) but if I left the page and came back and did not need to reload all the data, it did not work. While debugging, it seemed like I was setting the information for the map before it was finished loading.
So what I did to resolve the challenge was:
In the XAML - I added an event handler for the Loaded event of the map.
Example: Loaded="myMap_Loaded"
In the myMap_Loaded event, I simply called an async method to wait for the data to load then map
it.
Example:
private void myMap_Loaded(object sender, RoutedEventArgs e)
{
WaitAndLoadMap();
}
Coded the WaitAndLoadMap method to wait for the data to finish loading before loading the
map.
private async void WaitAndLoadMap()
{
//Check if the data is loaded and if it is not - loop.
while (!App.NearbyLocationsViewModel.IsLocationDataLoaded)
await Task.Delay(250);
//Load the map content and set the mapview.
}
It seems to be working. Hope this helps others.

Windows Phone App Freezing while loading main page?

My windows phone app is freezing while loading the main page. I have set breakpoints on the main contructor and it fires the OnNavigatedTo event but never fires the "Loaded" event. It gets through the InitializeComponent() in the contructor. It shows the splash screen and the mainpage application bar, but freezes at that point.
I have recently refactored my main namespace, which was causing the mainpage to not load. I fixed that via the Startup Object.
EVERYTHING was working before the refactoring.
What code should I include? The project is fairly large at this point, so I dont know how much you really want me posting code.
Any ideas??

Ok I found the problem. In App.Xaml.cs I made the following crucial mistake:
Here is my code:
private void CompleteInitializePhoneApplication(object sender, NavigationEventArgs e)
{
// Set the root visual to allow the application to render
if (RootVisual != null && RootVisual != RootFrame)
RootVisual = RootFrame;
// Remove this handler since it is no longer needed
RootFrame.Navigated -= CompleteInitializePhoneApplication;
}
And here is what is was supposed to be:
private void CompleteInitializePhoneApplication(object sender, NavigationEventArgs e)
{
// Set the root visual to allow the application to render
if (RootVisual != RootFrame)
RootVisual = RootFrame;
// Remove this handler since it is no longer needed
RootFrame.Navigated -= CompleteInitializePhoneApplication;
}
Resharper thought it would be best to check if RootVisual was null first. Incredibly irritating mistake as It would just hang at the startup PNG and never load, obviously because RootVisual wasn't being set.

I've had difficulties like this before. Sounds like it's probably a problem in your XAML but without actually having your solution it's hard to tell.
Here's a couple of things you could try:
Check all your static/dynamic resources to make sure that they're all still resolving correctly.
Check that any bindings and binding converters that you're using are still resolving properly. Converters in particular, I've had issues with them in the past.
If you're getting exceptions, but not tied to a specific point in code:
Try putting breakpoints on any or all custom properties that you might be using. Properties aren't stepped into by the debugger by default. I've found this to be the cause of a number of exceptions in my own work.
Hope this helps!

Paragraph.BringIntoView() works only when focused

I am working on a text editor that is based on RichEditBox. I have implemented functionality "Go to line" which eventually resolves to
TextPointer.Paragraph.BringIntoView();
Along with this I also set the caret position.
What I found out is that BringIntoView only works when I click on the RichEditBox first (focus it). Otherwise it seems to get ignored. I can see that the caret position has been adjusted by the code around BringIntoView though.
Does anybody know what is the reason/nature of that problem? How can I overcome it?

Found a workaround for this, not sure if it will work in a pure WPF environment, in my case I'm running WPF inside a mainly Windows Forms solution using WPF UserControls where needed.
Instead of invoking BringIntoFocus() immediately, defer it to a later moment by adding it to a queue that gets handled by a timer. For example:
System.Windows.Forms.Timer DeferredActionTimer = new System.Windows.Forms.Timer() { Interval = 200 };
Queue<Action> DeferredActions = new Queue<Action>();
void DeferredActionTimer_Tick(object sender, EventArgs e) {
while(DeferredActions.Count > 0) {
Action act = DeferredActions.Dequeue();
act();
}
}
In your forms constructor, or in the OnLoad event add:
DeferredActionTimer.Tick += new EventHandler(DeferredActionTimer_Tick);
DeferredActionTimer.Enabled = true;
Finally, instead of calling TextPointer.Paragraph.BringIntoView(); directly, call it like this:
DeferredActions.Enqueue(() => TextPointer.Paragraph.BringIntoView());
Note that the Windows Forms timer kicks events off in the main thread (via the message pump loop). If you have to use another timer you need a bit of extra code. I'd recommend you to use System.Timers.Timer rather than the System.Threading.Timer (it's a little more thread-safe). You would also have to wrap the action in a Dispatcher.Invoke structure. In my case, the WinForms timer works like a charm.

Can't you just give the RichTextBox(?) focus first then, using Keyboard.Focus(richTextBox) or richTextBox.Focus()?