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Unexpected behavior in async method

I am currently experiencing some unexpected/unwanted behavior with an aync method I am trying to use. The async method is RecognizeAsync. I am unabled to await this method since it returns void. What is happening, is that ProcessAudio method will be called first and will seemingly run to completion however the webpage never returns my "Contact" view as it should or errors out. After the method runs to completion, the breakpoints in my handlers start being hit. If I let it play through to completion, no redirect will ever happen- in the network tab in chrome debugger, the "status" will stay marked as pending and just hang there. I believe my issue is being caused by issues with asynchronousity but have been unable to found out what exactly it is.
All help is appreciated.
[HttpPost]
public async Task<ActionResult> ProcessAudio()
{
SpeechRecognitionEngine speechEngine = new SpeechRecognitionEngine();
speechEngine.SetInputToWaveFile(Server.MapPath("~/Content/AudioAssets/speechSample.wav"));
var grammar = new DictationGrammar();
speechEngine.LoadGrammar(grammar);
speechEngine.SpeechRecognized += new EventHandler<SpeechRecognizedEventArgs>(SpeechRecognizedHandler);
speechEngine.SpeechHypothesized += new EventHandler<SpeechHypothesizedEventArgs>(SpeechHypothesizedHandler);
speechEngine.RecognizeAsync(RecognizeMode.Multiple);
return View("Contact", vm); //first breakpoint hit occurs on this line
//but it doesnt seem to be executed?
}
private void SpeechRecognizedHandler(object sender, EventArgs e)
{
//do some work
//3rd breakpoint is hit here
}
private void SpeechHypothesizedHandler(object sender, EventArgs e)
{
//do some different work
//2nd breakpoint is hit here
}
UPDATE: based on suggestions, I have changed my code to (in ProcessAudio):
using (speechEngine)
{
speechEngine.SetInputToWaveFile(Server.MapPath("~/Content/AudioAssets/speechSample.wav"));
var grammar = new DictationGrammar();
speechEngine.LoadGrammar(grammar);
speechEngine.SpeechRecognized += new EventHandler<SpeechRecognizedEventArgs>(SpeechRecognizedHandler);
speechEngine.SpeechHypothesized += new EventHandler<SpeechHypothesizedEventArgs>(SpeechHypothesizedHandler);
var tcsRecognized = new TaskCompletionSource<EventArgs>();
speechEngine.RecognizeCompleted += (sender, eventArgs) => tcsRecognized.SetResult(eventArgs);
speechEngine.RecognizeAsync(RecognizeMode.Multiple);
try
{
var eventArgsRecognized = await tcsRecognized.Task;
}
catch(Exception e)
{
throw (e);
}
}
and this is resulting in some wrong behavior:
The return View("Contact",vm) breakpoint will now be hit AFTER the handlers are finished firing however there is still no redirect that ever happens. I am never directed to my Contact page. I just si ton my original page indefinitely just like before.

You're going too early. The speech engine probably hasn't even started by the time you hit the return View line.
You need to wait until the final event is fired from the speech engine. The best approach would be to convert from the event based asynchrony to TAP-based asynchrony.
This can be achieved by using TaskCompletionSource<T>
Let's deal with (what I believe) should be the last event to fire after speechEngine.RecognizeAsync is called, i.e. SpeechRecognized. I'm assuming that this is the event that fires when the final result has been calculated by the speech engine.
So, first:
var tcs = new TaskCompletionSource<EventArgs>();
now lets hook it up to complete when SpeechRecognized is fired, using inline lambda-style method declaration:
speechEngine.SpeechRecognized += (sender, eventArgs) => tcs.SetResult(eventArgs);
(...wait... what happens if no speech was recognized? We'll also need to hook up the SpeechRecognitionRejected event and define a custom Exception subclass for this type of event... here I'll just call it RecognitionFailedException. Now we're trapping all possible outcomes of the recognition process, so we would hope that the TaskCompletionSource would complete in all outcomes.)
speechEngine.SpeechRecognitionRejected += (sender, eventArgs) =>
tcs.SetException(new RecognitionFailedException());
then
speechEngine.RecognizeAsync(RecognizeMode.Multiple);
now, we can await the Task property of our TaskCompletionSource:
try
{
var eventArgs = await tcs.Task;
}
catch(RecognitionFailedException ex)
{
//this would signal that nothing was recognized
}
do some processing on the EventArgs that is the Task's result, and return a viable result back to the client.
In the process of doing this, you are creating IDisposable instances that will need to be properly disposed.
So:
using(SpeechRecognitionEngine speechEngine = new SpeechRecognitionEngine())
{
//use the speechEngine with TaskCompletionSource
//wait until it's finished
try
{
var eventArgs = await tcs.Task;
}
catch(RecognitionFailedException ex)
{
//this would signal that nothing was recognized
}
} //dispose

if anyone is curious- i solved my issue by doing the following:
I changed to using Recognize() instead of RecognizeAsync(..) which lead to InvalidOperationException due to async events trying to be executed at an "invalid time in the pages lifecycle". To overcome this, I wrapped my operations in a thread and joined the thread back to the main thread directly after running it. Code below:
using (speechEngine)
{
var t = new Thread(() =>
{
speechEngine.SetInputToWaveFile(#"C:\AudioAssets\speechSample.wav");
speechEngine.LoadGrammar(dictationGrammar);
speechEngine.SpeechRecognized += new EventHandler<SpeechRecognizedEventArgs>(SpeechRecognizedHandler);
speechEngine.SpeechHypothesized += new EventHandler<SpeechHypothesizedEventArgs>(SpeechHypothesizedHandler);
speechEngine.Recognize();
});
t.Start();
t.Join();
}
}

Backgroundworker is always busy

I'm new to using event handlers and backgroundworkers, so I may be missing something completely obvious here. Still, I've been trying to fix this for two days, so I thought I might as well see what anyone had to say.
I have a backgroundworker called SqlExpressDownloader. It starts running at the beginning of my program, the rest of the work runs, and then it should wait for the operations in the SqlExpressDownloader_DoWork() method to complete before continuing. The only problem is that for some reason whenever I do while(SqlExpressDownloader.IsBusy), it always responds as busy and therefore will wait forever.
The code for the event handler is here:
private void SqlExpressDownloader_DoWork(object sender, DoWorkEventArgs e)
{
string sSource = string.Format("{0}\\{1}", Paths.Settings_Common, "sqlexpr_x64_enu.exe");
Debug.WriteLine(sSource);
Debug.WriteLine("http://www.elexioamp.com/Install/redistributables/sql2008r2express/sqlexpr_x64_enu.exe");
if (!System.IO.File.Exists(sSource))
{
WebClient oWebClient = new WebClient();
oWebClient.DownloadProgressChanged += DownloadProgressChanged;
oWebClient.DownloadDataCompleted += DownloadComplete;
oWebClient.DownloadFileAsync(new System.Uri("http://www.elexioamp.com/Install/redistributables/sql2008r2express/sqlexpr_x64_enu.exe"), sSource);
while (oWebClient.IsBusy)
{
Thread.Sleep(100);
}
e.Result = "";
DownloadFinished = true;
}
}
I have watched the code and have watched it complete this method. I even added a return after the DownloadFinished = true, but it still responds as busy. What I want to know is how to make the backgroundworker respond as not busy.
EDIT
The events are all added in the constructor as shown here:
SqlExpressDownloader = new BackgroundWorker();
SqlExpressDownloader.DoWork += new DoWorkEventHandler(this.SqlExpressDownloader_DoWork);
SqlExpressDownloader.RunWorkerCompleted += new RunWorkerCompletedEventHandler(this.SqlExpressDownloader_RunWorkerCompleted);
The RunWorkerCompleteEventHandler looks like this:
private void SqlExpressDownloader_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Error != null)
{
Debug.WriteLine("The actions are complete.");
}
else
{
Debug.WriteLine("Error in completed work.");
}
}
But, when I debugged it last, it didn't actually trigger.

Instead of querying SqlExpressDownloader.IsBusy in a loop, try subscribing to the RunWorkerCompleted event of the BackgroundWorker and place your code in there that should only occur after the DoWork event has completed.
You'll also have access to the RunWorkerCompletedEventArgs, which you can check to make sure no error was thrown from the DoWork portion of your BackgroundWorker.
...
...
SqlExpressDownloader.RunWorkerCompleted += SqlExpressDownloader_RunWorkerCompleted;
SqlExpressDownloader.RunWorkerAsync();
}
private void SqlExpressDownloader_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Error != null)
{
// do something in response to the error
}
// stuff to do after DoWork has completed
}
I found Joe Albahari's tutorial helpful when I was learning how to use these.

You can replace your code with more elegant async/await solution like this
private async Task SqlExpressDownloadAsync()
{
string sSource = string.Format("{0}\\{1}", Paths.Settings_Common, "sqlexpr_x64_enu.exe");
Debug.WriteLine(sSource);
Debug.WriteLine("http://www.elexioamp.com/Install/redistributables/sql2008r2express/sqlexpr_x64_enu.exe");
if (!System.IO.File.Exists(sSource))
{
WebClient oWebClient = new WebClient();
oWebClient.DownloadProgressChanged += DownloadProgressChanged;
oWebClient.DownloadDataCompleted += DownloadComplete;
await oWebClient.DownloadFileTaskAsync(new System.Uri("http://www.elexioamp.com/Install/redistributables/sql2008r2express/sqlexpr_x64_enu.exe"), sSource);
}
}

I had a similar issue. DownloadASync would fire but .IsBusy would always stay on true.
This probably won't be a common problem, just thought I share my resolution.
I used
MessageBox.Show(new Form() { TopMost = true }, "", "")
This was the cause. I also tried:
var t = new Form() { TopMost = true };
MessageBox.Show(t, "", "");
t.Dispose();
This caused the same issue.
My code had multiple threads, I assume one of them must have gotten stuck, or perhaps the MessageBox(the new Form() { TopMost = true; } ) call created a stuck thread.
As soon as I removed that part, eg.
MessageBox.Show("", "");
Everything worked as expected again.
So maybe you are creating another thread somewhere that is causing your issue.

C# "InvalidCastException" when trying to access webbrowser control from TimerCallback

Basically I have the same problem as this user:
How to check for TrackBar sliding with mouse hold and release
I fixed this using the first solution provided. However, when the timer is called, I want to call InvokeScript on a webbrowser control. InvokeScript runs without an error, but the javascript function is never called. When I call this script from like a button clicked event handler, the function is called properly.
I found out that when I try to access properties from the webbrowser control (like MessageBox.Show(webBrowser1.DocumentText), this throws a InvalidCastException.
// in constructor:
webBrowser1.AllowWebBrowserDrop = false;
webBrowser1.IsWebBrowserContextMenuEnabled = false;
webBrowser1.WebBrowserShortcutsEnabled = false;
webBrowser1.ObjectForScripting = this;
timer = new System.Threading.Timer(this.TimerElapsed);
private void trackBar2_ValueChanged(object sender, EventArgs e)
{
timer.Change(500, -1);
}
private void TimerElapsed(object state)
{
this.webBrowser1.InvokeScript("jmp_end");
MessageBox.Show(this.webBrowser1.DocumentText);
timerRunning = false;
}
private void TimerElapsed(object state)
{
WebBrowser brw = getBrowser();
brw.Document.InvokeScript("jmpend");
MessageBox.Show(brw.DocumentText);
timerRunning = false;
}
Does anyone know what I am doing wrong here? Or is there another way to get the same result?
After comments about InvokeRequired, this sounds exactly like what I need.. But I can't get it working.. This is what I made from the sample code from C# System.InvalidCastException
public delegate WebBrowser getBrowserHandler();
public WebBrowser getBrowser()
{
if (InvokeRequired)
{
return Invoke(new getBrowserHandler(getBrowser)) as WebBrowser;
}
else
{
return webBrowser1;
}
}
private void TimerElapsed(object state)
{
WebBrowser brw = getBrowser();
brw.Document.InvokeScript("jmpend");
MessageBox.Show(brw.DocumentText);
timerRunning = false;
}
What have I missed here?

The caller (the timer) is on a different thread than the control was created on.
See Control.InvokeRequired Property
Sample code that should address your issue is posted on this question: C# System.InvalidCastException

I had the same problem. As pointed out by Kevin P. Rice, the caller is on a diferente thread than the one the control was created on. A simple solution for this is to use this.Invoke() everytime the thread needs to interact with a control, therefore, if you desire to have the browser invoke a script, and you wish to call it from inside a separate thread, just do it like this:
this.Invoke(new Action(() => { brw.Document.InvokeScript("jmpend"); }));
Or if you wish to change the property of the browse or another control within the form:
this.Invoke(new Action(() => { button1.Enabled = false; }));
If the declaration of your thread is in another scope than that of your form, and you can't use the this keyword, you need to find a way to reference the current instance of the form.
I hope this helps. :)

C# WebBrowser Button Click, then go to another page

I need to click an html button and navigate to another page. After click I need to wait for page loading, and go to the new page only when the old page loaded.
Here is the code, that click a button:
element = webBrowser1.Document.GetElementById("LoginButton");
element.InvokeMember("click");
webBrowser has got a IsBusy property, but it don`t works after button click:
element = webBrowser1.Document.GetElementById("LoginButton");
element.InvokeMember("click");
if(webBrowser1.IsBusy)
{
MessageBox.Show("Busy"); // Nothing happens, but page is not full loaded.
}
If I add System.Threading.Thread.Sleep(1000) the page loads and I can go to next page, but page loading time on other computers can be more.
What can I do to load another page only after the previous page has loaded?
P.S: I am from Russia, so sorry for bad English.

If your webpage has any javascript blocks, you won't be able to solve the problem using the WebBrowser control itself. You should wait for a document.ready event using javascript code and let know your C# program about it.
Previously, I made a javascript block that provides the webpage state. It looks like this:
var isBusy = true;
function getIsScriptBusy () {
return isBusy;
}
// when loading is complete:
// isBusy = false;
// document.ready event, for example
and a C# code that waits for it to return true:
void WaitForCallback(int timeout) {
Stopwatch w = new Stopwatch();
w.Start();
Wait(delegate() {
return (string)Document.InvokeScript("getIsScriptBusy") != "false"
&& (w.ElapsedMilliseconds < timeout || Debugger.IsAttached);
});
if(w.ElapsedMilliseconds >= timeout && !Debugger.IsAttached)
throw new Exception("Operation timed out.");
}
void Wait(WaitDelegate waitCondition) {
int bRet;
MSG msg = new MSG();
while(waitCondition() && (bRet = GetMessage(ref msg, new HandleRef(null, IntPtr.Zero), 0, 0)) != 0) {
if(bRet == -1) {
// handle the error and possibly exit
} else {
TranslateMessage(ref msg);
DispatchMessage(ref msg);
}
Thread.Sleep(0);
}
}

There are lots of events exposed by the WebBrowser control. You might try Navigated or DocumentCompleted.
Nick

WebBrowser.Navigated is the browser event you are seeking.

Use this ,
You might just be able to use this once
br1.DocumentCompleted += br1_DocumentCompleted;
Application.Run();
Call
void br1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
var br1 = sender as WebBrowser;
if (br1.Url == e.Url)
{
Console.WriteLine("Natigated to {0}", e.Url);
Application.ExitThread(); // Stops the thread
}
}
Replace br1 with your webbrowser name
Hope this helps

InvokeMember("click") doesn't work in webBrowser control inside a thread

I am trying to create a multi-threaded application that creates WebBrowsers and does specific things to each one. When I tried my code from the main thread it worked great, However, When I changed the code to run from a thread, the code runs fine until InvokeMember("click") is called and nothing happens. InvokeMember() isn't executed and the button click doesn't take place. Here is my code:
private void button1_Click(object sender, EventArgs e)
{
Thread t = new Thread(Work);
t.SetApartmentState(ApartmentState.STA);
t.Start();
}
[STAThread]
void Work()
{
WebBrowser wb = new WebBrowser();
wb.ScriptErrorsSuppressed = false;
wb.Visible = true;
wb.Navigate("http://website.com");
while (wb.ReadyState != WebBrowserReadyState.Complete)
{
Application.DoEvents();
}
//updateText("Loaded");
wb.Document.GetElementById("F1").SetAttribute("Value", "Test");
wb.Document.GetElementById("F2").SetAttribute("Value", "Saracostaz");
wb.Document.GetElementById("F3").SetAttribute("Value", "Tester5123#hotmail.com");
wb.Document.GetElementById("F4").SetAttribute("Value", "Tester5123#hotmail.com");
wb.Document.GetElementById("F5").SetAttribute("Value", "limewire");
wb.Document.GetElementById("F6").SetAttribute("SelectedIndex", "1");
wb.Document.GetElementById("F7").SetAttribute("SelectedIndex", "2");
wb.Document.GetElementById("F8").SetAttribute("SelectedIndex", "5");
wb.Document.GetElementById("F9").SetAttribute("SelectedIndex", "20");
// updateText("Entered Data");
HtmlElementCollection elements = wb.Document.Body.All;
foreach (HtmlElement element in elements)
{
string valueAttribute = element.GetAttribute("value");
if (!string.IsNullOrEmpty(valueAttribute) && valueAttribute == "Sign Up")
{
element.InvokeMember("click");
//MessageBox.show("I am in"); //that messagebox shows normally.
break;
}
}
}
Please note that the Work() runs very correctly when it's called from the main thread. The problem lies in calling it from another thread.
Thanks in advance.

You are violating a hard requirement for an STA thread, it must pump a message loop. You patched your way out of trouble with the Navigate method by calling Application.DoEvents(). That pumps the message loop. But you are not doing this for InvokeClick.
Check this answer for the solution. Put the code in the DocumentCompleted event. There is no obvious way I see to decide when to stop the thread, you'd have to poll for some kind of side-effect of the click with a timer perhaps.

JFYI, you can do next using LINQ:
var element = elements
.OfType<HtmlElement>()
.Select(element => element.GetAttribute("value"))
.FirstOrDefault(value=> String.Equals(value, "Sign Up"));
if (element != null)
element.InvokeMember("click");